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diff --git a/extras/README b/extras/README deleted file mode 100644 index e642704..0000000 --- a/extras/README +++ /dev/null @@ -1,2 +0,0 @@ -Based on PKZIP appnotes, which are included here. - diff --git a/extras/zip-appnote-6.3.1-20070411.txt b/extras/zip-appnote-6.3.1-20070411.txt deleted file mode 100644 index 97fd591..0000000 --- a/extras/zip-appnote-6.3.1-20070411.txt +++ /dev/null @@ -1,3071 +0,0 @@ -source: http://www.pkware.com/documents/casestudies/APPNOTE.TXT - -File: APPNOTE.TXT - .ZIP File Format Specification -Version: 6.3.1 -Revised: April 11, 2007 -Copyright (c) 1989 - 2007 PKWARE Inc., All Rights Reserved. - -The use of certain technological aspects disclosed in the current -APPNOTE is available pursuant to the below section entitled -"Incorporating PKWARE Proprietary Technology into Your Product". - -I. Purpose ----------- - -This specification is intended to define a cross-platform, -interoperable file storage and transfer format. Since its -first publication in 1989, PKWARE has remained committed to -ensuring the interoperability of the .ZIP file format through -publication and maintenance of this specification. We trust that -all .ZIP compatible vendors and application developers that have -adopted and benefited from this format will share and support -this commitment to interoperability. - -II. Contacting PKWARE ---------------------- - - PKWARE, Inc. - 648 N. Plankinton Avenue, Suite 220 - Milwaukee, WI 53203 - +1-414-289-9788 - +1-414-289-9789 FAX - zipformat@pkware.com - -III. Disclaimer ---------------- - -Although PKWARE will attempt to supply current and accurate -information relating to its file formats, algorithms, and the -subject programs, the possibility of error or omission cannot -be eliminated. PKWARE therefore expressly disclaims any warranty -that the information contained in the associated materials relating -to the subject programs and/or the format of the files created or -accessed by the subject programs and/or the algorithms used by -the subject programs, or any other matter, is current, correct or -accurate as delivered. Any risk of damage due to any possible -inaccurate information is assumed by the user of the information. -Furthermore, the information relating to the subject programs -and/or the file formats created or accessed by the subject -programs and/or the algorithms used by the subject programs is -subject to change without notice. - -If the version of this file is marked as a NOTIFICATION OF CHANGE, -the content defines an Early Feature Specification (EFS) change -to the .ZIP file format that may be subject to modification prior -to publication of the Final Feature Specification (FFS). This -document may also contain information on Planned Feature -Specifications (PFS) defining recognized future extensions. - -IV. Change Log --------------- - -Version Change Description Date -------- ------------------ ---------- -5.2 -Single Password Symmetric Encryption 06/02/2003 - storage - -6.1.0 -Smartcard compatibility 01/20/2004 - -Documentation on certificate storage - -6.2.0 -Introduction of Central Directory 04/26/2004 - Encryption for encrypting metadata - -Added OS/X to Version Made By values - -6.2.1 -Added Extra Field placeholder for 04/01/2005 - POSZIP using ID 0x4690 - - -Clarified size field on - "zip64 end of central directory record" - -6.2.2 -Documented Final Feature Specification 01/06/2006 - for Strong Encryption - - -Clarifications and typographical - corrections - -6.3.0 -Added tape positioning storage 09/29/2006 - parameters - - -Expanded list of supported hash algorithms - - -Expanded list of supported compression - algorithms - - -Expanded list of supported encryption - algorithms - - -Added option for Unicode filename - storage - - -Clarifications for consistent use - of Data Descriptor records - - -Added additional "Extra Field" - definitions - -6.3.1 -Corrected standard hash values for 04/11/2007 - SHA-256/384/512 - - -V. General Format of a .ZIP file --------------------------------- - - Files stored in arbitrary order. Large .ZIP files can span multiple - volumes or be split into user-defined segment sizes. All values - are stored in little-endian byte order unless otherwise specified. - - Overall .ZIP file format: - - [local file header 1] - [file data 1] - [data descriptor 1] - . - . - . - [local file header n] - [file data n] - [data descriptor n] - [archive decryption header] - [archive extra data record] - [central directory] - [zip64 end of central directory record] - [zip64 end of central directory locator] - [end of central directory record] - - - A. Local file header: - - local file header signature 4 bytes (0x04034b50) - version needed to extract 2 bytes - general purpose bit flag 2 bytes - compression method 2 bytes - last mod file time 2 bytes - last mod file date 2 bytes - crc-32 4 bytes - compressed size 4 bytes - uncompressed size 4 bytes - file name length 2 bytes - extra field length 2 bytes - - file name (variable size) - extra field (variable size) - - B. File data - - Immediately following the local header for a file - is the compressed or stored data for the file. - The series of [local file header][file data][data - descriptor] repeats for each file in the .ZIP archive. - - C. Data descriptor: - - crc-32 4 bytes - compressed size 4 bytes - uncompressed size 4 bytes - - This descriptor exists only if bit 3 of the general - purpose bit flag is set (see below). It is byte aligned - and immediately follows the last byte of compressed data. - This descriptor is used only when it was not possible to - seek in the output .ZIP file, e.g., when the output .ZIP file - was standard output or a non-seekable device. For ZIP64(tm) format - archives, the compressed and uncompressed sizes are 8 bytes each. - - When compressing files, compressed and uncompressed sizes - should be stored in ZIP64 format (as 8 byte values) when a - files size exceeds 0xFFFFFFFF. However ZIP64 format may be - used regardless of the size of a file. When extracting, if - the zip64 extended information extra field is present for - the file the compressed and uncompressed sizes will be 8 - byte values. - - Although not originally assigned a signature, the value - 0x08074b50 has commonly been adopted as a signature value - for the data descriptor record. Implementers should be - aware that ZIP files may be encountered with or without this - signature marking data descriptors and should account for - either case when reading ZIP files to ensure compatibility. - When writing ZIP files, it is recommended to include the - signature value marking the data descriptor record. When - the signature is used, the fields currently defined for - the data descriptor record will immediately follow the - signature. - - An extensible data descriptor will be released in a future - version of this APPNOTE. This new record is intended to - resolve conflicts with the use of this record going forward, - and to provide better support for streamed file processing. - - When the Central Directory Encryption method is used, the data - descriptor record is not required, but may be used. If present, - and bit 3 of the general purpose bit field is set to indicate - its presence, the values in fields of the data descriptor - record should be set to binary zeros. - - D. Archive decryption header: - - The Archive Decryption Header is introduced in version 6.2 - of the ZIP format specification. This record exists in support - of the Central Directory Encryption Feature implemented as part of - the Strong Encryption Specification as described in this document. - When the Central Directory Structure is encrypted, this decryption - header will precede the encrypted data segment. The encrypted - data segment will consist of the Archive extra data record (if - present) and the encrypted Central Directory Structure data. - The format of this data record is identical to the Decryption - header record preceding compressed file data. If the central - directory structure is encrypted, the location of the start of - this data record is determined using the Start of Central Directory - field in the Zip64 End of Central Directory record. Refer to the - section on the Strong Encryption Specification for information - on the fields used in the Archive Decryption Header record. - - - E. Archive extra data record: - - archive extra data signature 4 bytes (0x08064b50) - extra field length 4 bytes - extra field data (variable size) - - The Archive Extra Data Record is introduced in version 6.2 - of the ZIP format specification. This record exists in support - of the Central Directory Encryption Feature implemented as part of - the Strong Encryption Specification as described in this document. - When present, this record immediately precedes the central - directory data structure. The size of this data record will be - included in the Size of the Central Directory field in the - End of Central Directory record. If the central directory structure - is compressed, but not encrypted, the location of the start of - this data record is determined using the Start of Central Directory - field in the Zip64 End of Central Directory record. - - - F. Central directory structure: - - [file header 1] - . - . - . - [file header n] - [digital signature] - - File header: - - central file header signature 4 bytes (0x02014b50) - version made by 2 bytes - version needed to extract 2 bytes - general purpose bit flag 2 bytes - compression method 2 bytes - last mod file time 2 bytes - last mod file date 2 bytes - crc-32 4 bytes - compressed size 4 bytes - uncompressed size 4 bytes - file name length 2 bytes - extra field length 2 bytes - file comment length 2 bytes - disk number start 2 bytes - internal file attributes 2 bytes - external file attributes 4 bytes - relative offset of local header 4 bytes - - file name (variable size) - extra field (variable size) - file comment (variable size) - - Digital signature: - - header signature 4 bytes (0x05054b50) - size of data 2 bytes - signature data (variable size) - - With the introduction of the Central Directory Encryption - feature in version 6.2 of this specification, the Central - Directory Structure may be stored both compressed and encrypted. - Although not required, it is assumed when encrypting the - Central Directory Structure, that it will be compressed - for greater storage efficiency. Information on the - Central Directory Encryption feature can be found in the section - describing the Strong Encryption Specification. The Digital - Signature record will be neither compressed nor encrypted. - - G. Zip64 end of central directory record - - zip64 end of central dir - signature 4 bytes (0x06064b50) - size of zip64 end of central - directory record 8 bytes - version made by 2 bytes - version needed to extract 2 bytes - number of this disk 4 bytes - number of the disk with the - start of the central directory 4 bytes - total number of entries in the - central directory on this disk 8 bytes - total number of entries in the - central directory 8 bytes - size of the central directory 8 bytes - offset of start of central - directory with respect to - the starting disk number 8 bytes - zip64 extensible data sector (variable size) - - The value stored into the "size of zip64 end of central - directory record" should be the size of the remaining - record and should not include the leading 12 bytes. - - Size = SizeOfFixedFields + SizeOfVariableData - 12. - - The above record structure defines Version 1 of the - zip64 end of central directory record. Version 1 was - implemented in versions of this specification preceding - 6.2 in support of the ZIP64 large file feature. The - introduction of the Central Directory Encryption feature - implemented in version 6.2 as part of the Strong Encryption - Specification defines Version 2 of this record structure. - Refer to the section describing the Strong Encryption - Specification for details on the version 2 format for - this record. - - Special purpose data may reside in the zip64 extensible data - sector field following either a V1 or V2 version of this - record. To ensure identification of this special purpose data - it must include an identifying header block consisting of the - following: - - Header ID - 2 bytes - Data Size - 4 bytes - - The Header ID field indicates the type of data that is in the - data block that follows. - - Data Size identifies the number of bytes that follow for this - data block type. - - Multiple special purpose data blocks may be present, but each - must be preceded by a Header ID and Data Size field. Current - mappings of Header ID values supported in this field are as - defined in APPENDIX C. - - H. Zip64 end of central directory locator - - zip64 end of central dir locator - signature 4 bytes (0x07064b50) - number of the disk with the - start of the zip64 end of - central directory 4 bytes - relative offset of the zip64 - end of central directory record 8 bytes - total number of disks 4 bytes - - I. End of central directory record: - - end of central dir signature 4 bytes (0x06054b50) - number of this disk 2 bytes - number of the disk with the - start of the central directory 2 bytes - total number of entries in the - central directory on this disk 2 bytes - total number of entries in - the central directory 2 bytes - size of the central directory 4 bytes - offset of start of central - directory with respect to - the starting disk number 4 bytes - .ZIP file comment length 2 bytes - .ZIP file comment (variable size) - - J. Explanation of fields: - - version made by (2 bytes) - - The upper byte indicates the compatibility of the file - attribute information. If the external file attributes - are compatible with MS-DOS and can be read by PKZIP for - DOS version 2.04g then this value will be zero. If these - attributes are not compatible, then this value will - identify the host system on which the attributes are - compatible. Software can use this information to determine - the line record format for text files etc. The current - mappings are: - - 0 - MS-DOS and OS/2 (FAT / VFAT / FAT32 file systems) - 1 - Amiga 2 - OpenVMS - 3 - UNIX 4 - VM/CMS - 5 - Atari ST 6 - OS/2 H.P.F.S. - 7 - Macintosh 8 - Z-System - 9 - CP/M 10 - Windows NTFS - 11 - MVS (OS/390 - Z/OS) 12 - VSE - 13 - Acorn Risc 14 - VFAT - 15 - alternate MVS 16 - BeOS - 17 - Tandem 18 - OS/400 - 19 - OS/X (Darwin) 20 thru 255 - unused - - The lower byte indicates the ZIP specification version - (the version of this document) supported by the software - used to encode the file. The value/10 indicates the major - version number, and the value mod 10 is the minor version - number. - - version needed to extract (2 bytes) - - The minimum supported ZIP specification version needed to - extract the file, mapped as above. This value is based on - the specific format features a ZIP program must support to - be able to extract the file. If multiple features are - applied to a file, the minimum version should be set to the - feature having the highest value. New features or feature - changes affecting the published format specification will be - implemented using higher version numbers than the last - published value to avoid conflict. - - Current minimum feature versions are as defined below: - - 1.0 - Default value - 1.1 - File is a volume label - 2.0 - File is a folder (directory) - 2.0 - File is compressed using Deflate compression - 2.0 - File is encrypted using traditional PKWARE encryption - 2.1 - File is compressed using Deflate64(tm) - 2.5 - File is compressed using PKWARE DCL Implode - 2.7 - File is a patch data set - 4.5 - File uses ZIP64 format extensions - 4.6 - File is compressed using BZIP2 compression* - 5.0 - File is encrypted using DES - 5.0 - File is encrypted using 3DES - 5.0 - File is encrypted using original RC2 encryption - 5.0 - File is encrypted using RC4 encryption - 5.1 - File is encrypted using AES encryption - 5.1 - File is encrypted using corrected RC2 encryption** - 5.2 - File is encrypted using corrected RC2-64 encryption** - 6.1 - File is encrypted using non-OAEP key wrapping*** - 6.2 - Central directory encryption - 6.3 - File is compressed using LZMA - 6.3 - File is compressed using PPMd+ - 6.3 - File is encrypted using Blowfish - 6.3 - File is encrypted using Twofish - - - * Early 7.x (pre-7.2) versions of PKZIP incorrectly set the - version needed to extract for BZIP2 compression to be 50 - when it should have been 46. - - ** Refer to the section on Strong Encryption Specification - for additional information regarding RC2 corrections. - - *** Certificate encryption using non-OAEP key wrapping is the - intended mode of operation for all versions beginning with 6.1. - Support for OAEP key wrapping should only be used for - backward compatibility when sending ZIP files to be opened by - versions of PKZIP older than 6.1 (5.0 or 6.0). - - + Files compressed using PPMd should set the version - needed to extract field to 6.3, however, not all ZIP - programs enforce this and may be unable to decompress - data files compressed using PPMd if this value is set. - - When using ZIP64 extensions, the corresponding value in the - zip64 end of central directory record should also be set. - This field should be set appropriately to indicate whether - Version 1 or Version 2 format is in use. - - general purpose bit flag: (2 bytes) - - Bit 0: If set, indicates that the file is encrypted. - - (For Method 6 - Imploding) - Bit 1: If the compression method used was type 6, - Imploding, then this bit, if set, indicates - an 8K sliding dictionary was used. If clear, - then a 4K sliding dictionary was used. - Bit 2: If the compression method used was type 6, - Imploding, then this bit, if set, indicates - 3 Shannon-Fano trees were used to encode the - sliding dictionary output. If clear, then 2 - Shannon-Fano trees were used. - - (For Methods 8 and 9 - Deflating) - Bit 2 Bit 1 - 0 0 Normal (-en) compression option was used. - 0 1 Maximum (-exx/-ex) compression option was used. - 1 0 Fast (-ef) compression option was used. - 1 1 Super Fast (-es) compression option was used. - - (For Method 14 - LZMA) - Bit 1: If the compression method used was type 14, - LZMA, then this bit, if set, indicates - an end-of-stream (EOS) marker is used to - mark the end of the compressed data stream. - If clear, then an EOS marker is not present - and the compressed data size must be known - to extract. - - Note: Bits 1 and 2 are undefined if the compression - method is any other. - - Bit 3: If this bit is set, the fields crc-32, compressed - size and uncompressed size are set to zero in the - local header. The correct values are put in the - data descriptor immediately following the compressed - data. (Note: PKZIP version 2.04g for DOS only - recognizes this bit for method 8 compression, newer - versions of PKZIP recognize this bit for any - compression method.) - - Bit 4: Reserved for use with method 8, for enhanced - deflating. - - Bit 5: If this bit is set, this indicates that the file is - compressed patched data. (Note: Requires PKZIP - version 2.70 or greater) - - Bit 6: Strong encryption. If this bit is set, you should - set the version needed to extract value to at least - 50 and you must also set bit 0. If AES encryption - is used, the version needed to extract value must - be at least 51. - - Bit 7: Currently unused. - - Bit 8: Currently unused. - - Bit 9: Currently unused. - - Bit 10: Currently unused. - - Bit 11: Language encoding flag (EFS). If this bit is set, - the filename and comment fields for this file - must be encoded using UTF-8. (see APPENDIX D) - - Bit 12: Reserved by PKWARE for enhanced compression. - - Bit 13: Used when encrypting the Central Directory to indicate - selected data values in the Local Header are masked to - hide their actual values. See the section describing - the Strong Encryption Specification for details. - - Bit 14: Reserved by PKWARE. - - Bit 15: Reserved by PKWARE. - - compression method: (2 bytes) - - (see accompanying documentation for algorithm - descriptions) - - 0 - The file is stored (no compression) - 1 - The file is Shrunk - 2 - The file is Reduced with compression factor 1 - 3 - The file is Reduced with compression factor 2 - 4 - The file is Reduced with compression factor 3 - 5 - The file is Reduced with compression factor 4 - 6 - The file is Imploded - 7 - Reserved for Tokenizing compression algorithm - 8 - The file is Deflated - 9 - Enhanced Deflating using Deflate64(tm) - 10 - PKWARE Data Compression Library Imploding (old IBM TERSE) - 11 - Reserved by PKWARE - 12 - File is compressed using BZIP2 algorithm - 13 - Reserved by PKWARE - 14 - LZMA (EFS) - 15 - Reserved by PKWARE - 16 - Reserved by PKWARE - 17 - Reserved by PKWARE - 18 - File is compressed using IBM TERSE (new) - 19 - IBM LZ77 z Architecture (PFS) - 98 - PPMd version I, Rev 1 - - date and time fields: (2 bytes each) - - The date and time are encoded in standard MS-DOS format. - If input came from standard input, the date and time are - those at which compression was started for this data. - If encrypting the central directory and general purpose bit - flag 13 is set indicating masking, the value stored in the - Local Header will be zero. - - CRC-32: (4 bytes) - - The CRC-32 algorithm was generously contributed by - David Schwaderer and can be found in his excellent - book "C Programmers Guide to NetBIOS" published by - Howard W. Sams & Co. Inc. The 'magic number' for - the CRC is 0xdebb20e3. The proper CRC pre and post - conditioning is used, meaning that the CRC register - is pre-conditioned with all ones (a starting value - of 0xffffffff) and the value is post-conditioned by - taking the one's complement of the CRC residual. - If bit 3 of the general purpose flag is set, this - field is set to zero in the local header and the correct - value is put in the data descriptor and in the central - directory. When encrypting the central directory, if the - local header is not in ZIP64 format and general purpose - bit flag 13 is set indicating masking, the value stored - in the Local Header will be zero. - - compressed size: (4 bytes) - uncompressed size: (4 bytes) - - The size of the file compressed and uncompressed, - respectively. When a decryption header is present it will - be placed in front of the file data and the value of the - compressed file size will include the bytes of the decryption - header. If bit 3 of the general purpose bit flag is set, - these fields are set to zero in the local header and the - correct values are put in the data descriptor and - in the central directory. If an archive is in ZIP64 format - and the value in this field is 0xFFFFFFFF, the size will be - in the corresponding 8 byte ZIP64 extended information - extra field. When encrypting the central directory, if the - local header is not in ZIP64 format and general purpose bit - flag 13 is set indicating masking, the value stored for the - uncompressed size in the Local Header will be zero. - - file name length: (2 bytes) - extra field length: (2 bytes) - file comment length: (2 bytes) - - The length of the file name, extra field, and comment - fields respectively. The combined length of any - directory record and these three fields should not - generally exceed 65,535 bytes. If input came from standard - input, the file name length is set to zero. - - disk number start: (2 bytes) - - The number of the disk on which this file begins. If an - archive is in ZIP64 format and the value in this field is - 0xFFFF, the size will be in the corresponding 4 byte zip64 - extended information extra field. - - internal file attributes: (2 bytes) - - Bits 1 and 2 are reserved for use by PKWARE. - - The lowest bit of this field indicates, if set, that - the file is apparently an ASCII or text file. If not - set, that the file apparently contains binary data. - The remaining bits are unused in version 1.0. - - The 0x0002 bit of this field indicates, if set, that a - 4 byte variable record length control field precedes each - logical record indicating the length of the record. The - record length control field is stored in little-endian byte - order. This flag is independent of text control characters, - and if used in conjunction with text data, includes any - control characters in the total length of the record. This - value is provided for mainframe data transfer support. - - external file attributes: (4 bytes) - - The mapping of the external attributes is - host-system dependent (see 'version made by'). For - MS-DOS, the low order byte is the MS-DOS directory - attribute byte. If input came from standard input, this - field is set to zero. - - relative offset of local header: (4 bytes) - - This is the offset from the start of the first disk on - which this file appears, to where the local header should - be found. If an archive is in ZIP64 format and the value - in this field is 0xFFFFFFFF, the size will be in the - corresponding 8 byte zip64 extended information extra field. - - file name: (Variable) - - The name of the file, with optional relative path. - The path stored should not contain a drive or - device letter, or a leading slash. All slashes - should be forward slashes '/' as opposed to - backwards slashes '\' for compatibility with Amiga - and UNIX file systems etc. If input came from standard - input, there is no file name field. If encrypting - the central directory and general purpose bit flag 13 is set - indicating masking, the file name stored in the Local Header - will not be the actual file name. A masking value consisting - of a unique hexadecimal value will be stored. This value will - be sequentially incremented for each file in the archive. See - the section on the Strong Encryption Specification for details - on retrieving the encrypted file name. - - extra field: (Variable) - - This is for expansion. If additional information - needs to be stored for special needs or for specific - platforms, it should be stored here. Earlier versions - of the software can then safely skip this file, and - find the next file or header. This field will be 0 - length in version 1.0. - - In order to allow different programs and different types - of information to be stored in the 'extra' field in .ZIP - files, the following structure should be used for all - programs storing data in this field: - - header1+data1 + header2+data2 . . . - - Each header should consist of: - - Header ID - 2 bytes - Data Size - 2 bytes - - Note: all fields stored in Intel low-byte/high-byte order. - - The Header ID field indicates the type of data that is in - the following data block. - - Header ID's of 0 thru 31 are reserved for use by PKWARE. - The remaining ID's can be used by third party vendors for - proprietary usage. - - The current Header ID mappings defined by PKWARE are: - - 0x0001 Zip64 extended information extra field - 0x0007 AV Info - 0x0008 Reserved for extended language encoding data (PFS) - (see APPENDIX D) - 0x0009 OS/2 - 0x000a NTFS - 0x000c OpenVMS - 0x000d UNIX - 0x000e Reserved for file stream and fork descriptors - 0x000f Patch Descriptor - 0x0014 PKCS#7 Store for X.509 Certificates - 0x0015 X.509 Certificate ID and Signature for - individual file - 0x0016 X.509 Certificate ID for Central Directory - 0x0017 Strong Encryption Header - 0x0018 Record Management Controls - 0x0019 PKCS#7 Encryption Recipient Certificate List - 0x0065 IBM S/390 (Z390), AS/400 (I400) attributes - - uncompressed - 0x0066 Reserved for IBM S/390 (Z390), AS/400 (I400) - attributes - compressed - 0x4690 POSZIP 4690 (reserved) - - Third party mappings commonly used are: - - - 0x07c8 Macintosh - 0x2605 ZipIt Macintosh - 0x2705 ZipIt Macintosh 1.3.5+ - 0x2805 ZipIt Macintosh 1.3.5+ - 0x334d Info-ZIP Macintosh - 0x4341 Acorn/SparkFS - 0x4453 Windows NT security descriptor (binary ACL) - 0x4704 VM/CMS - 0x470f MVS - 0x4b46 FWKCS MD5 (see below) - 0x4c41 OS/2 access control list (text ACL) - 0x4d49 Info-ZIP OpenVMS - 0x4f4c Xceed original location extra field - 0x5356 AOS/VS (ACL) - 0x5455 extended timestamp - 0x554e Xceed unicode extra field - 0x5855 Info-ZIP UNIX (original, also OS/2, NT, etc) - 0x6542 BeOS/BeBox - 0x756e ASi UNIX - 0x7855 Info-ZIP UNIX (new) - 0xa220 Microsoft Open Packaging Growth Hint - 0xfd4a SMS/QDOS - - Detailed descriptions of Extra Fields defined by third - party mappings will be documented as information on - these data structures is made available to PKWARE. - PKWARE does not guarantee the accuracy of any published - third party data. - - The Data Size field indicates the size of the following - data block. Programs can use this value to skip to the - next header block, passing over any data blocks that are - not of interest. - - Note: As stated above, the size of the entire .ZIP file - header, including the file name, comment, and extra - field should not exceed 64K in size. - - In case two different programs should appropriate the same - Header ID value, it is strongly recommended that each - program place a unique signature of at least two bytes in - size (and preferably 4 bytes or bigger) at the start of - each data area. Every program should verify that its - unique signature is present, in addition to the Header ID - value being correct, before assuming that it is a block of - known type. - - -Zip64 Extended Information Extra Field (0x0001): - - The following is the layout of the zip64 extended - information "extra" block. If one of the size or - offset fields in the Local or Central directory - record is too small to hold the required data, - a Zip64 extended information record is created. - The order of the fields in the zip64 extended - information record is fixed, but the fields will - only appear if the corresponding Local or Central - directory record field is set to 0xFFFF or 0xFFFFFFFF. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (ZIP64) 0x0001 2 bytes Tag for this "extra" block type - Size 2 bytes Size of this "extra" block - Original - Size 8 bytes Original uncompressed file size - Compressed - Size 8 bytes Size of compressed data - Relative Header - Offset 8 bytes Offset of local header record - Disk Start - Number 4 bytes Number of the disk on which - this file starts - - This entry in the Local header must include BOTH original - and compressed file size fields. If encrypting the - central directory and bit 13 of the general purpose bit - flag is set indicating masking, the value stored in the - Local Header for the original file size will be zero. - - - -OS/2 Extra Field (0x0009): - - The following is the layout of the OS/2 attributes "extra" - block. (Last Revision 09/05/95) - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (OS/2) 0x0009 2 bytes Tag for this "extra" block type - TSize 2 bytes Size for the following data block - BSize 4 bytes Uncompressed Block Size - CType 2 bytes Compression type - EACRC 4 bytes CRC value for uncompress block - (var) variable Compressed block - - The OS/2 extended attribute structure (FEA2LIST) is - compressed and then stored in it's entirety within this - structure. There will only ever be one "block" of data in - VarFields[]. - - -NTFS Extra Field (0x000a): - - The following is the layout of the NTFS attributes - "extra" block. (Note: At this time the Mtime, Atime - and Ctime values may be used on any WIN32 system.) - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (NTFS) 0x000a 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of the total "extra" block - Reserved 4 bytes Reserved for future use - Tag1 2 bytes NTFS attribute tag value #1 - Size1 2 bytes Size of attribute #1, in bytes - (var.) Size1 Attribute #1 data - . - . - . - TagN 2 bytes NTFS attribute tag value #N - SizeN 2 bytes Size of attribute #N, in bytes - (var.) SizeN Attribute #N data - - For NTFS, values for Tag1 through TagN are as follows: - (currently only one set of attributes is defined for NTFS) - - Tag Size Description - ----- ---- ----------- - 0x0001 2 bytes Tag for attribute #1 - Size1 2 bytes Size of attribute #1, in bytes - Mtime 8 bytes File last modification time - Atime 8 bytes File last access time - Ctime 8 bytes File creation time - - -OpenVMS Extra Field (0x000c): - - The following is the layout of the OpenVMS attributes - "extra" block. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (VMS) 0x000c 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of the total "extra" block - CRC 4 bytes 32-bit CRC for remainder of the block - Tag1 2 bytes OpenVMS attribute tag value #1 - Size1 2 bytes Size of attribute #1, in bytes - (var.) Size1 Attribute #1 data - . - . - . - TagN 2 bytes OpenVMS attribute tag value #N - SizeN 2 bytes Size of attribute #N, in bytes - (var.) SizeN Attribute #N data - - Rules: - - 1. There will be one or more of attributes present, which - will each be preceded by the above TagX & SizeX values. - These values are identical to the ATR$C_XXXX and - ATR$S_XXXX constants which are defined in ATR.H under - OpenVMS C. Neither of these values will ever be zero. - - 2. No word alignment or padding is performed. - - 3. A well-behaved PKZIP/OpenVMS program should never produce - more than one sub-block with the same TagX value. Also, - there will never be more than one "extra" block of type - 0x000c in a particular directory record. - - -UNIX Extra Field (0x000d): - - The following is the layout of the UNIX "extra" block. - Note: all fields are stored in Intel low-byte/high-byte - order. - - Value Size Description - ----- ---- ----------- - (UNIX) 0x000d 2 bytes Tag for this "extra" block type - TSize 2 bytes Size for the following data block - Atime 4 bytes File last access time - Mtime 4 bytes File last modification time - Uid 2 bytes File user ID - Gid 2 bytes File group ID - (var) variable Variable length data field - - The variable length data field will contain file type - specific data. Currently the only values allowed are - the original "linked to" file names for hard or symbolic - links, and the major and minor device node numbers for - character and block device nodes. Since device nodes - cannot be either symbolic or hard links, only one set of - variable length data is stored. Link files will have the - name of the original file stored. This name is NOT NULL - terminated. Its size can be determined by checking TSize - - 12. Device entries will have eight bytes stored as two 4 - byte entries (in little endian format). The first entry - will be the major device number, and the second the minor - device number. - - -PATCH Descriptor Extra Field (0x000f): - - The following is the layout of the Patch Descriptor "extra" - block. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (Patch) 0x000f 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of the total "extra" block - Version 2 bytes Version of the descriptor - Flags 4 bytes Actions and reactions (see below) - OldSize 4 bytes Size of the file about to be patched - OldCRC 4 bytes 32-bit CRC of the file to be patched - NewSize 4 bytes Size of the resulting file - NewCRC 4 bytes 32-bit CRC of the resulting file - - Actions and reactions - - Bits Description - ---- ---------------- - 0 Use for auto detection - 1 Treat as a self-patch - 2-3 RESERVED - 4-5 Action (see below) - 6-7 RESERVED - 8-9 Reaction (see below) to absent file - 10-11 Reaction (see below) to newer file - 12-13 Reaction (see below) to unknown file - 14-15 RESERVED - 16-31 RESERVED - - Actions - - Action Value - ------ ----- - none 0 - add 1 - delete 2 - patch 3 - - Reactions - - Reaction Value - -------- ----- - ask 0 - skip 1 - ignore 2 - fail 3 - - Patch support is provided by PKPatchMaker(tm) technology and is - covered under U.S. Patents and Patents Pending. The use or - implementation in a product of certain technological aspects set - forth in the current APPNOTE, including those with regard to - strong encryption, patching, or extended tape operations requires - a license from PKWARE. Please contact PKWARE with regard to - acquiring a license. - - -PKCS#7 Store for X.509 Certificates (0x0014): - - This field contains information about each of the certificates - files may be signed with. When the Central Directory Encryption - feature is enabled for a ZIP file, this record will appear in - the Archive Extra Data Record, otherwise it will appear in the - first central directory record and will be ignored in any - other record. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (Store) 0x0014 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of the store data - TData TSize Data about the store - - - -X.509 Certificate ID and Signature for individual file (0x0015): - - This field contains the information about which certificate in - the PKCS#7 store was used to sign a particular file. It also - contains the signature data. This field can appear multiple - times, but can only appear once per certificate. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (CID) 0x0015 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of data that follows - TData TSize Signature Data - - -X.509 Certificate ID and Signature for central directory (0x0016): - - This field contains the information about which certificate in - the PKCS#7 store was used to sign the central directory structure. - When the Central Directory Encryption feature is enabled for a - ZIP file, this record will appear in the Archive Extra Data Record, - otherwise it will appear in the first central directory record. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (CDID) 0x0016 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of data that follows - TData TSize Data - - -Strong Encryption Header (0x0017): - - Value Size Description - ----- ---- ----------- - 0x0017 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of data that follows - Format 2 bytes Format definition for this record - AlgID 2 bytes Encryption algorithm identifier - Bitlen 2 bytes Bit length of encryption key - Flags 2 bytes Processing flags - CertData TSize-8 Certificate decryption extra field data - (refer to the explanation for CertData - in the section describing the - Certificate Processing Method under - the Strong Encryption Specification) - - - -Record Management Controls (0x0018): - - Value Size Description - ----- ---- ----------- -(Rec-CTL) 0x0018 2 bytes Tag for this "extra" block type - CSize 2 bytes Size of total extra block data - Tag1 2 bytes Record control attribute 1 - Size1 2 bytes Size of attribute 1, in bytes - Data1 Size1 Attribute 1 data - . - . - . - TagN 2 bytes Record control attribute N - SizeN 2 bytes Size of attribute N, in bytes - DataN SizeN Attribute N data - - - -PKCS#7 Encryption Recipient Certificate List (0x0019): - - This field contains information about each of the certificates - used in encryption processing and it can be used to identify who is - allowed to decrypt encrypted files. This field should only appear - in the archive extra data record. This field is not required and - serves only to aide archive modifications by preserving public - encryption key data. Individual security requirements may dictate - that this data be omitted to deter information exposure. - - Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - (CStore) 0x0019 2 bytes Tag for this "extra" block type - TSize 2 bytes Size of the store data - TData TSize Data about the store - - TData: - - Value Size Description - ----- ---- ----------- - Version 2 bytes Format version number - must 0x0001 at this time - CStore (var) PKCS#7 data blob - - - -MVS Extra Field (0x0065): - - The following is the layout of the MVS "extra" block. - Note: Some fields are stored in Big Endian format. - All text is in EBCDIC format unless otherwise specified. - - Value Size Description - ----- ---- ----------- - (MVS) 0x0065 2 bytes Tag for this "extra" block type - TSize 2 bytes Size for the following data block - ID 4 bytes EBCDIC "Z390" 0xE9F3F9F0 or - "T4MV" for TargetFour - (var) TSize-4 Attribute data (see APPENDIX B) - - - -OS/400 Extra Field (0x0065): - - The following is the layout of the OS/400 "extra" block. - Note: Some fields are stored in Big Endian format. - All text is in EBCDIC format unless otherwise specified. - - Value Size Description - ----- ---- ----------- - (OS400) 0x0065 2 bytes Tag for this "extra" block type - TSize 2 bytes Size for the following data block - ID 4 bytes EBCDIC "I400" 0xC9F4F0F0 or - "T4MV" for TargetFour - (var) TSize-4 Attribute data (see APPENDIX A) - - - Third-party Mappings: - - -ZipIt Macintosh Extra Field (long) (0x2605): - - The following is the layout of the ZipIt extra block - for Macintosh. The local-header and central-header versions - are identical. This block must be present if the file is - stored MacBinary-encoded and it should not be used if the file - is not stored MacBinary-encoded. - - Value Size Description - ----- ---- ----------- - (Mac2) 0x2605 Short tag for this extra block type - TSize Short total data size for this block - "ZPIT" beLong extra-field signature - FnLen Byte length of FileName - FileName variable full Macintosh filename - FileType Byte[4] four-byte Mac file type string - Creator Byte[4] four-byte Mac creator string - - - -ZipIt Macintosh Extra Field (short, for files) (0x2705): - - The following is the layout of a shortened variant of the - ZipIt extra block for Macintosh (without "full name" entry). - This variant is used by ZipIt 1.3.5 and newer for entries of - files (not directories) that do not have a MacBinary encoded - file. The local-header and central-header versions are identical. - - Value Size Description - ----- ---- ----------- - (Mac2b) 0x2705 Short tag for this extra block type - TSize Short total data size for this block (12) - "ZPIT" beLong extra-field signature - FileType Byte[4] four-byte Mac file type string - Creator Byte[4] four-byte Mac creator string - fdFlags beShort attributes from FInfo.frFlags, - may be omitted - 0x0000 beShort reserved, may be omitted - - - -ZipIt Macintosh Extra Field (short, for directories) (0x2805): - - The following is the layout of a shortened variant of the - ZipIt extra block for Macintosh used only for directory - entries. This variant is used by ZipIt 1.3.5 and newer to - save some optional Mac-specific information about directories. - The local-header and central-header versions are identical. - - Value Size Description - ----- ---- ----------- - (Mac2c) 0x2805 Short tag for this extra block type - TSize Short total data size for this block (12) - "ZPIT" beLong extra-field signature - frFlags beShort attributes from DInfo.frFlags, may - be omitted - View beShort ZipIt view flag, may be omitted - - - The View field specifies ZipIt-internal settings as follows: - - Bits of the Flags: - bit 0 if set, the folder is shown expanded (open) - when the archive contents are viewed in ZipIt. - bits 1-15 reserved, zero; - - - -FWKCS MD5 Extra Field (0x4b46): - - The FWKCS Contents_Signature System, used in - automatically identifying files independent of file name, - optionally adds and uses an extra field to support the - rapid creation of an enhanced contents_signature: - - Header ID = 0x4b46 - Data Size = 0x0013 - Preface = 'M','D','5' - followed by 16 bytes containing the uncompressed file's - 128_bit MD5 hash(1), low byte first. - - When FWKCS revises a .ZIP file central directory to add - this extra field for a file, it also replaces the - central directory entry for that file's uncompressed - file length with a measured value. - - FWKCS provides an option to strip this extra field, if - present, from a .ZIP file central directory. In adding - this extra field, FWKCS preserves .ZIP file Authenticity - Verification; if stripping this extra field, FWKCS - preserves all versions of AV through PKZIP version 2.04g. - - FWKCS, and FWKCS Contents_Signature System, are - trademarks of Frederick W. Kantor. - - (1) R. Rivest, RFC1321.TXT, MIT Laboratory for Computer - Science and RSA Data Security, Inc., April 1992. - ll.76-77: "The MD5 algorithm is being placed in the - public domain for review and possible adoption as a - standard." - - -Microsoft Open Packaging Growth Hint (0xa220): - - Value Size Description - ----- ---- ----------- - 0xa220 Short tag for this extra block type - TSize Short size of Sig + PadVal + Padding - Sig Short verification signature (A028) - PadVal Short Initial padding value - Padding variable filled with NULL characters - - - file comment: (Variable) - - The comment for this file. - - number of this disk: (2 bytes) - - The number of this disk, which contains central - directory end record. If an archive is in ZIP64 format - and the value in this field is 0xFFFF, the size will - be in the corresponding 4 byte zip64 end of central - directory field. - - - number of the disk with the start of the central - directory: (2 bytes) - - The number of the disk on which the central - directory starts. If an archive is in ZIP64 format - and the value in this field is 0xFFFF, the size will - be in the corresponding 4 byte zip64 end of central - directory field. - - total number of entries in the central dir on - this disk: (2 bytes) - - The number of central directory entries on this disk. - If an archive is in ZIP64 format and the value in - this field is 0xFFFF, the size will be in the - corresponding 8 byte zip64 end of central - directory field. - - total number of entries in the central dir: (2 bytes) - - The total number of files in the .ZIP file. If an - archive is in ZIP64 format and the value in this field - is 0xFFFF, the size will be in the corresponding 8 byte - zip64 end of central directory field. - - size of the central directory: (4 bytes) - - The size (in bytes) of the entire central directory. - If an archive is in ZIP64 format and the value in - this field is 0xFFFFFFFF, the size will be in the - corresponding 8 byte zip64 end of central - directory field. - - offset of start of central directory with respect to - the starting disk number: (4 bytes) - - Offset of the start of the central directory on the - disk on which the central directory starts. If an - archive is in ZIP64 format and the value in this - field is 0xFFFFFFFF, the size will be in the - corresponding 8 byte zip64 end of central - directory field. - - .ZIP file comment length: (2 bytes) - - The length of the comment for this .ZIP file. - - .ZIP file comment: (Variable) - - The comment for this .ZIP file. ZIP file comment data - is stored unsecured. No encryption or data authentication - is applied to this area at this time. Confidential information - should not be stored in this section. - - zip64 extensible data sector (variable size) - - (currently reserved for use by PKWARE) - - - K. Splitting and Spanning ZIP files - - Spanning is the process of segmenting a ZIP file across - multiple removable media. This support has typically only - been provided for DOS formatted floppy diskettes. - - File splitting is a newer derivative of spanning. - Splitting follows the same segmentation process as - spanning, however, it does not require writing each - segment to a unique removable medium and instead supports - placing all pieces onto local or non-removable locations - such as file systems, local drives, folders, etc... - - A key difference between spanned and split ZIP files is - that all pieces of a spanned ZIP file have the same name. - Since each piece is written to a separate volume, no name - collisions occur and each segment can reuse the original - .ZIP file name given to the archive. - - Sequence ordering for DOS spanned archives uses the DOS - volume label to determine segment numbers. Volume labels - for each segment are written using the form PKBACK#xxx, - where xxx is the segment number written as a decimal - value from 001 - nnn. - - Split ZIP files are typically written to the same location - and are subject to name collisions if the spanned name - format is used since each segment will reside on the same - drive. To avoid name collisions, split archives are named - as follows. - - Segment 1 = filename.z01 - Segment n-1 = filename.z(n-1) - Segment n = filename.zip - - The .ZIP extension is used on the last segment to support - quickly reading the central directory. The segment number - n should be a decimal value. - - Spanned ZIP files may be PKSFX Self-extracting ZIP files. - PKSFX files may also be split, however, in this case - the first segment must be named filename.exe. The first - segment of a split PKSFX archive must be large enough to - include the entire executable program. - - Capacities for split archives are as follows. - - Maximum number of segments = 4,294,967,295 - 1 - Maximum .ZIP segment size = 4,294,967,295 bytes - Minimum segment size = 64K - Maximum PKSFX segment size = 2,147,483,647 bytes - - Segment sizes may be different however by convention, all - segment sizes should be the same with the exception of the - last, which may be smaller. Local and central directory - header records must never be split across a segment boundary. - When writing a header record, if the number of bytes remaining - within a segment is less than the size of the header record, - end the current segment and write the header at the start - of the next segment. The central directory may span segment - boundaries, but no single record in the central directory - should be split across segments. - - Spanned/Split archives created using PKZIP for Windows - (V2.50 or greater), PKZIP Command Line (V2.50 or greater), - or PKZIP Explorer will include a special spanning - signature as the first 4 bytes of the first segment of - the archive. This signature (0x08074b50) will be - followed immediately by the local header signature for - the first file in the archive. - - A special spanning marker may also appear in spanned/split - archives if the spanning or splitting process starts but - only requires one segment. In this case the 0x08074b50 - signature will be replaced with the temporary spanning - marker signature of 0x30304b50. Split archives can - only be uncompressed by other versions of PKZIP that - know how to create a split archive. - - The signature value 0x08074b50 is also used by some - ZIP implementations as a marker for the Data Descriptor - record. Conflict in this alternate assignment can be - avoided by ensuring the position of the signature - within the ZIP file to determine the use for which it - is intended. - - L. General notes: - - 1) All fields unless otherwise noted are unsigned and stored - in Intel low-byte:high-byte, low-word:high-word order. - - 2) String fields are not null terminated, since the - length is given explicitly. - - 3) The entries in the central directory may not necessarily - be in the same order that files appear in the .ZIP file. - - 4) If one of the fields in the end of central directory - record is too small to hold required data, the field - should be set to -1 (0xFFFF or 0xFFFFFFFF) and the - ZIP64 format record should be created. - - 5) The end of central directory record and the - Zip64 end of central directory locator record must - reside on the same disk when splitting or spanning - an archive. - -VI. UnShrinking - Method 1 --------------------------- - -Shrinking is a Dynamic Ziv-Lempel-Welch compression algorithm -with partial clearing. The initial code size is 9 bits, and -the maximum code size is 13 bits. Shrinking differs from -conventional Dynamic Ziv-Lempel-Welch implementations in several -respects: - -1) The code size is controlled by the compressor, and is not - automatically increased when codes larger than the current - code size are created (but not necessarily used). When - the decompressor encounters the code sequence 256 - (decimal) followed by 1, it should increase the code size - read from the input stream to the next bit size. No - blocking of the codes is performed, so the next code at - the increased size should be read from the input stream - immediately after where the previous code at the smaller - bit size was read. Again, the decompressor should not - increase the code size used until the sequence 256,1 is - encountered. - -2) When the table becomes full, total clearing is not - performed. Rather, when the compressor emits the code - sequence 256,2 (decimal), the decompressor should clear - all leaf nodes from the Ziv-Lempel tree, and continue to - use the current code size. The nodes that are cleared - from the Ziv-Lempel tree are then re-used, with the lowest - code value re-used first, and the highest code value - re-used last. The compressor can emit the sequence 256,2 - at any time. - -VII. Expanding - Methods 2-5 ----------------------------- - -The Reducing algorithm is actually a combination of two -distinct algorithms. The first algorithm compresses repeated -byte sequences, and the second algorithm takes the compressed -stream from the first algorithm and applies a probabilistic -compression method. - -The probabilistic compression stores an array of 'follower -sets' S(j), for j=0 to 255, corresponding to each possible -ASCII character. Each set contains between 0 and 32 -characters, to be denoted as S(j)[0],...,S(j)[m], where m<32. -The sets are stored at the beginning of the data area for a -Reduced file, in reverse order, with S(255) first, and S(0) -last. - -The sets are encoded as { N(j), S(j)[0],...,S(j)[N(j)-1] }, -where N(j) is the size of set S(j). N(j) can be 0, in which -case the follower set for S(j) is empty. Each N(j) value is -encoded in 6 bits, followed by N(j) eight bit character values -corresponding to S(j)[0] to S(j)[N(j)-1] respectively. If -N(j) is 0, then no values for S(j) are stored, and the value -for N(j-1) immediately follows. - -Immediately after the follower sets, is the compressed data -stream. The compressed data stream can be interpreted for the -probabilistic decompression as follows: - -let Last-Character <- 0. -loop until done - if the follower set S(Last-Character) is empty then - read 8 bits from the input stream, and copy this - value to the output stream. - otherwise if the follower set S(Last-Character) is non-empty then - read 1 bit from the input stream. - if this bit is not zero then - read 8 bits from the input stream, and copy this - value to the output stream. - otherwise if this bit is zero then - read B(N(Last-Character)) bits from the input - stream, and assign this value to I. - Copy the value of S(Last-Character)[I] to the - output stream. - - assign the last value placed on the output stream to - Last-Character. -end loop - -B(N(j)) is defined as the minimal number of bits required to -encode the value N(j)-1. - -The decompressed stream from above can then be expanded to -re-create the original file as follows: - -let State <- 0. - -loop until done - read 8 bits from the input stream into C. - case State of - 0: if C is not equal to DLE (144 decimal) then - copy C to the output stream. - otherwise if C is equal to DLE then - let State <- 1. - - 1: if C is non-zero then - let V <- C. - let Len <- L(V) - let State <- F(Len). - otherwise if C is zero then - copy the value 144 (decimal) to the output stream. - let State <- 0 - - 2: let Len <- Len + C - let State <- 3. - - 3: move backwards D(V,C) bytes in the output stream - (if this position is before the start of the output - stream, then assume that all the data before the - start of the output stream is filled with zeros). - copy Len+3 bytes from this position to the output stream. - let State <- 0. - end case -end loop - -The functions F,L, and D are dependent on the 'compression -factor', 1 through 4, and are defined as follows: - -For compression factor 1: - L(X) equals the lower 7 bits of X. - F(X) equals 2 if X equals 127 otherwise F(X) equals 3. - D(X,Y) equals the (upper 1 bit of X) * 256 + Y + 1. -For compression factor 2: - L(X) equals the lower 6 bits of X. - F(X) equals 2 if X equals 63 otherwise F(X) equals 3. - D(X,Y) equals the (upper 2 bits of X) * 256 + Y + 1. -For compression factor 3: - L(X) equals the lower 5 bits of X. - F(X) equals 2 if X equals 31 otherwise F(X) equals 3. - D(X,Y) equals the (upper 3 bits of X) * 256 + Y + 1. -For compression factor 4: - L(X) equals the lower 4 bits of X. - F(X) equals 2 if X equals 15 otherwise F(X) equals 3. - D(X,Y) equals the (upper 4 bits of X) * 256 + Y + 1. - -VIII. Imploding - Method 6 --------------------------- - -The Imploding algorithm is actually a combination of two distinct -algorithms. The first algorithm compresses repeated byte -sequences using a sliding dictionary. The second algorithm is -used to compress the encoding of the sliding dictionary output, -using multiple Shannon-Fano trees. - -The Imploding algorithm can use a 4K or 8K sliding dictionary -size. The dictionary size used can be determined by bit 1 in the -general purpose flag word; a 0 bit indicates a 4K dictionary -while a 1 bit indicates an 8K dictionary. - -The Shannon-Fano trees are stored at the start of the compressed -file. The number of trees stored is defined by bit 2 in the -general purpose flag word; a 0 bit indicates two trees stored, a -1 bit indicates three trees are stored. If 3 trees are stored, -the first Shannon-Fano tree represents the encoding of the -Literal characters, the second tree represents the encoding of -the Length information, the third represents the encoding of the -Distance information. When 2 Shannon-Fano trees are stored, the -Length tree is stored first, followed by the Distance tree. - -The Literal Shannon-Fano tree, if present is used to represent -the entire ASCII character set, and contains 256 values. This -tree is used to compress any data not compressed by the sliding -dictionary algorithm. When this tree is present, the Minimum -Match Length for the sliding dictionary is 3. If this tree is -not present, the Minimum Match Length is 2. - -The Length Shannon-Fano tree is used to compress the Length part -of the (length,distance) pairs from the sliding dictionary -output. The Length tree contains 64 values, ranging from the -Minimum Match Length, to 63 plus the Minimum Match Length. - -The Distance Shannon-Fano tree is used to compress the Distance -part of the (length,distance) pairs from the sliding dictionary -output. The Distance tree contains 64 values, ranging from 0 to -63, representing the upper 6 bits of the distance value. The -distance values themselves will be between 0 and the sliding -dictionary size, either 4K or 8K. - -The Shannon-Fano trees themselves are stored in a compressed -format. The first byte of the tree data represents the number of -bytes of data representing the (compressed) Shannon-Fano tree -minus 1. The remaining bytes represent the Shannon-Fano tree -data encoded as: - - High 4 bits: Number of values at this bit length + 1. (1 - 16) - Low 4 bits: Bit Length needed to represent value + 1. (1 - 16) - -The Shannon-Fano codes can be constructed from the bit lengths -using the following algorithm: - -1) Sort the Bit Lengths in ascending order, while retaining the - order of the original lengths stored in the file. - -2) Generate the Shannon-Fano trees: - - Code <- 0 - CodeIncrement <- 0 - LastBitLength <- 0 - i <- number of Shannon-Fano codes - 1 (either 255 or 63) - - loop while i >= 0 - Code = Code + CodeIncrement - if BitLength(i) <> LastBitLength then - LastBitLength=BitLength(i) - CodeIncrement = 1 shifted left (16 - LastBitLength) - ShannonCode(i) = Code - i <- i - 1 - end loop - -3) Reverse the order of all the bits in the above ShannonCode() - vector, so that the most significant bit becomes the least - significant bit. For example, the value 0x1234 (hex) would - become 0x2C48 (hex). - -4) Restore the order of Shannon-Fano codes as originally stored - within the file. - -Example: - - This example will show the encoding of a Shannon-Fano tree - of size 8. Notice that the actual Shannon-Fano trees used - for Imploding are either 64 or 256 entries in size. - -Example: 0x02, 0x42, 0x01, 0x13 - - The first byte indicates 3 values in this table. Decoding the - bytes: - 0x42 = 5 codes of 3 bits long - 0x01 = 1 code of 2 bits long - 0x13 = 2 codes of 4 bits long - - This would generate the original bit length array of: - (3, 3, 3, 3, 3, 2, 4, 4) - - There are 8 codes in this table for the values 0 thru 7. Using - the algorithm to obtain the Shannon-Fano codes produces: - - Reversed Order Original -Val Sorted Constructed Code Value Restored Length ---- ------ ----------------- -------- -------- ------ -0: 2 1100000000000000 11 101 3 -1: 3 1010000000000000 101 001 3 -2: 3 1000000000000000 001 110 3 -3: 3 0110000000000000 110 010 3 -4: 3 0100000000000000 010 100 3 -5: 3 0010000000000000 100 11 2 -6: 4 0001000000000000 1000 1000 4 -7: 4 0000000000000000 0000 0000 4 - -The values in the Val, Order Restored and Original Length columns -now represent the Shannon-Fano encoding tree that can be used for -decoding the Shannon-Fano encoded data. How to parse the -variable length Shannon-Fano values from the data stream is beyond -the scope of this document. (See the references listed at the end of -this document for more information.) However, traditional decoding -schemes used for Huffman variable length decoding, such as the -Greenlaw algorithm, can be successfully applied. - -The compressed data stream begins immediately after the -compressed Shannon-Fano data. The compressed data stream can be -interpreted as follows: - -loop until done - read 1 bit from input stream. - - if this bit is non-zero then (encoded data is literal data) - if Literal Shannon-Fano tree is present - read and decode character using Literal Shannon-Fano tree. - otherwise - read 8 bits from input stream. - copy character to the output stream. - otherwise (encoded data is sliding dictionary match) - if 8K dictionary size - read 7 bits for offset Distance (lower 7 bits of offset). - otherwise - read 6 bits for offset Distance (lower 6 bits of offset). - - using the Distance Shannon-Fano tree, read and decode the - upper 6 bits of the Distance value. - - using the Length Shannon-Fano tree, read and decode - the Length value. - - Length <- Length + Minimum Match Length - - if Length = 63 + Minimum Match Length - read 8 bits from the input stream, - add this value to Length. - - move backwards Distance+1 bytes in the output stream, and - copy Length characters from this position to the output - stream. (if this position is before the start of the output - stream, then assume that all the data before the start of - the output stream is filled with zeros). -end loop - -IX. Tokenizing - Method 7 -------------------------- - -This method is not used by PKZIP. - -X. Deflating - Method 8 ------------------------ - -The Deflate algorithm is similar to the Implode algorithm using -a sliding dictionary of up to 32K with secondary compression -from Huffman/Shannon-Fano codes. - -The compressed data is stored in blocks with a header describing -the block and the Huffman codes used in the data block. The header -format is as follows: - - Bit 0: Last Block bit This bit is set to 1 if this is the last - compressed block in the data. - Bits 1-2: Block type - 00 (0) - Block is stored - All stored data is byte aligned. - Skip bits until next byte, then next word = block - length, followed by the ones compliment of the block - length word. Remaining data in block is the stored - data. - - 01 (1) - Use fixed Huffman codes for literal and distance codes. - Lit Code Bits Dist Code Bits - --------- ---- --------- ---- - 0 - 143 8 0 - 31 5 - 144 - 255 9 - 256 - 279 7 - 280 - 287 8 - - Literal codes 286-287 and distance codes 30-31 are - never used but participate in the huffman construction. - - 10 (2) - Dynamic Huffman codes. (See expanding Huffman codes) - - 11 (3) - Reserved - Flag a "Error in compressed data" if seen. - -Expanding Huffman Codes ------------------------ -If the data block is stored with dynamic Huffman codes, the Huffman -codes are sent in the following compressed format: - - 5 Bits: # of Literal codes sent - 256 (256 - 286) - All other codes are never sent. - 5 Bits: # of Dist codes - 1 (1 - 32) - 4 Bits: # of Bit Length codes - 3 (3 - 19) - -The Huffman codes are sent as bit lengths and the codes are built as -described in the implode algorithm. The bit lengths themselves are -compressed with Huffman codes. There are 19 bit length codes: - - 0 - 15: Represent bit lengths of 0 - 15 - 16: Copy the previous bit length 3 - 6 times. - The next 2 bits indicate repeat length (0 = 3, ... ,3 = 6) - Example: Codes 8, 16 (+2 bits 11), 16 (+2 bits 10) will - expand to 12 bit lengths of 8 (1 + 6 + 5) - 17: Repeat a bit length of 0 for 3 - 10 times. (3 bits of length) - 18: Repeat a bit length of 0 for 11 - 138 times (7 bits of length) - -The lengths of the bit length codes are sent packed 3 bits per value -(0 - 7) in the following order: - - 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 - -The Huffman codes should be built as described in the Implode algorithm -except codes are assigned starting at the shortest bit length, i.e. the -shortest code should be all 0's rather than all 1's. Also, codes with -a bit length of zero do not participate in the tree construction. The -codes are then used to decode the bit lengths for the literal and -distance tables. - -The bit lengths for the literal tables are sent first with the number -of entries sent described by the 5 bits sent earlier. There are up -to 286 literal characters; the first 256 represent the respective 8 -bit character, code 256 represents the End-Of-Block code, the remaining -29 codes represent copy lengths of 3 thru 258. There are up to 30 -distance codes representing distances from 1 thru 32k as described -below. - - Length Codes - ------------ - Extra Extra Extra Extra - Code Bits Length Code Bits Lengths Code Bits Lengths Code Bits Length(s) - ---- ---- ------ ---- ---- ------- ---- ---- ------- ---- ---- --------- - 257 0 3 265 1 11,12 273 3 35-42 281 5 131-162 - 258 0 4 266 1 13,14 274 3 43-50 282 5 163-194 - 259 0 5 267 1 15,16 275 3 51-58 283 5 195-226 - 260 0 6 268 1 17,18 276 3 59-66 284 5 227-257 - 261 0 7 269 2 19-22 277 4 67-82 285 0 258 - 262 0 8 270 2 23-26 278 4 83-98 - 263 0 9 271 2 27-30 279 4 99-114 - 264 0 10 272 2 31-34 280 4 115-130 - - Distance Codes - -------------- - Extra Extra Extra Extra - Code Bits Dist Code Bits Dist Code Bits Distance Code Bits Distance - ---- ---- ---- ---- ---- ------ ---- ---- -------- ---- ---- -------- - 0 0 1 8 3 17-24 16 7 257-384 24 11 4097-6144 - 1 0 2 9 3 25-32 17 7 385-512 25 11 6145-8192 - 2 0 3 10 4 33-48 18 8 513-768 26 12 8193-12288 - 3 0 4 11 4 49-64 19 8 769-1024 27 12 12289-16384 - 4 1 5,6 12 5 65-96 20 9 1025-1536 28 13 16385-24576 - 5 1 7,8 13 5 97-128 21 9 1537-2048 29 13 24577-32768 - 6 2 9-12 14 6 129-192 22 10 2049-3072 - 7 2 13-16 15 6 193-256 23 10 3073-4096 - -The compressed data stream begins immediately after the -compressed header data. The compressed data stream can be -interpreted as follows: - -do - read header from input stream. - - if stored block - skip bits until byte aligned - read count and 1's compliment of count - copy count bytes data block - otherwise - loop until end of block code sent - decode literal character from input stream - if literal < 256 - copy character to the output stream - otherwise - if literal = end of block - break from loop - otherwise - decode distance from input stream - - move backwards distance bytes in the output stream, and - copy length characters from this position to the output - stream. - end loop -while not last block - -if data descriptor exists - skip bits until byte aligned - read crc and sizes -endif - -XI. Enhanced Deflating - Method 9 ---------------------------------- - -The Enhanced Deflating algorithm is similar to Deflate but -uses a sliding dictionary of up to 64K. Deflate64(tm) is supported -by the Deflate extractor. - -XII. BZIP2 - Method 12 ----------------------- - -BZIP2 is an open-source data compression algorithm developed by -Julian Seward. Information and source code for this algorithm -can be found on the internet. - -XIII. LZMA - Method 14 (EFS) ----------------------------- - -LZMA is a block-oriented, general purpose data compression algorithm -developed and maintained by Igor Pavlov. It is a derivative of LZ77 -that utilizes Markov chains and a range coder. Information and -source code for this algorithm can be found on the internet. Consult -with the author of this algorithm for information on terms or -restrictions on use. - -Support for LZMA within the ZIP format is defined as follows: - -The Compression method field within the ZIP Local and Central -Header records will be set to the value 14 to indicate data was -compressed using LZMA. - -The Version needed to extract field within the ZIP Local and -Central Header records will be set to 6.3 to indicate the -minimum ZIP format version supporting this feature. - -File data compressed using the LZMA algorithm must be placed -immediately following the Local Header for the file. If a -standard ZIP encryption header is required, it will follow -the Local Header and will precede the LZMA compressed file -data segment. The location of LZMA compressed data segment -within the ZIP format will be as shown: - - [local header file 1] - [encryption header file 1] - [LZMA compressed data segment for file 1] - [data descriptor 1] - [local header file 2] - -The encryption header and data descriptor records may -be conditionally present. The LZMA Compressed Data Segment -will consist of an LZMA Properties Header followed by the -LZMA Compressed Data as shown: - - [LZMA properties header for file 1] - [LZMA compressed data for file 1] - -The LZMA Compressed Data will be stored as provided by the -LZMA compression library. Compressed size, uncompressed -size and other file characteristics about the file being -compressed must be stored in standard ZIP storage format. - -The LZMA Properties Header will store specific data required to -decompress the LZMA compressed Data. This data is set by the -LZMA compression engine using the function WriteCoderProperties() -as documented within the LZMA SDK. - -Storage fields for the property information within the LZMA -Properties Header are as follows: - - LZMA Version Information 2 bytes - LZMA Properties Size 2 bytes - LZMA Properties Data variable, defined by "LZMA Properties Size" - -LZMA Version Information - this field identifies which version of - the LZMA SDK was used to compress a file. The first byte will - store the major version number of the LZMA SDK and the second - byte will store the minor number. - -LZMA Properties Size - this field defines the size of the remaining - property data. Typically this size should be determined by the - version of the SDK. This size field is included as a convenience - and to help avoid any ambiguity should it arise in the future due - to changes in this compression algorithm. - -LZMA Property Data - this variable sized field records the required - values for the decompressor as defined by the LZMA SDK. The - data stored in this field should be obtained using the - WriteCoderProperties() in the version of the SDK defined by - the "LZMA Version Information" field. - -The layout of the "LZMA Properties Data" field is a function of the -LZMA compression algorithm. It is possible that this layout may be -changed by the author over time. The data layout in version 4.32 -of the LZMA SDK defines a 5 byte array that uses 4 bytes to store -the dictionary size in little-endian order. This is preceded by a -single packed byte as the first element of the array that contains -the following fields: - - PosStateBits - LiteralPosStateBits - LiteralContextBits - -Refer to the LZMA documentation for a more detailed explanation of -these fields. - -Data compressed with method 14, LZMA, may include an end-of-stream -(EOS) marker ending the compressed data stream. This marker is not -required, but its use is highly recommended to facilitate processing -and implementers should include the EOS marker whenever possible. -When the EOS marker is used, general purpose bit 1 must be set. If -general purpose bit 1 is not set, the EOS marker is not present. - -XIV. PPMd - Method 98 ---------------------- - -PPMd is a data compression algorithm developed by Dmitry Shkarin -which includes a carryless rangecoder developed by Dmitry Subbotin. -This algorithm is based on predictive phrase matching on multiple -order contexts. Information and source code for this algorithm -can be found on the internet. Consult with the author of this -algorithm for information on terms or restrictions on use. - -Support for PPMd within the ZIP format currently is provided only -for version I, revision 1 of the algorithm. Storage requirements -for using this algorithm are as follows: - -Parameters needed to control the algorithm are stored in the two -bytes immediately preceding the compressed data. These bytes are -used to store the following fields: - -Model order - sets the maximum model order, default is 8, possible - values are from 2 to 16 inclusive - -Sub-allocator size - sets the size of sub-allocator in MB, default is 50, - possible values are from 1MB to 256MB inclusive - -Model restoration method - sets the method used to restart context - model at memory insufficiency, values are: - - 0 - restarts model from scratch - default - 1 - cut off model - decreases performance by as much as 2x - 2 - freeze context tree - not recommended - -An example for packing these fields into the 2 byte storage field is -illustrated below. These values are stored in Intel low-byte/high-byte -order. - -wPPMd = (Model order - 1) + - ((Sub-allocator size - 1) << 4) + - (Model restoration method << 12) - - -XV. Traditional PKWARE Encryption ---------------------------------- - -The following information discusses the decryption steps -required to support traditional PKWARE encryption. This -form of encryption is considered weak by today's standards -and its use is recommended only for situations with -low security needs or for compatibility with older .ZIP -applications. - -Decryption ----------- - -PKWARE is grateful to Mr. Roger Schlafly for his expert contribution -towards the development of PKWARE's traditional encryption. - -PKZIP encrypts the compressed data stream. Encrypted files must -be decrypted before they can be extracted. - -Each encrypted file has an extra 12 bytes stored at the start of -the data area defining the encryption header for that file. The -encryption header is originally set to random values, and then -itself encrypted, using three, 32-bit keys. The key values are -initialized using the supplied encryption password. After each byte -is encrypted, the keys are then updated using pseudo-random number -generation techniques in combination with the same CRC-32 algorithm -used in PKZIP and described elsewhere in this document. - -The following is the basic steps required to decrypt a file: - -1) Initialize the three 32-bit keys with the password. -2) Read and decrypt the 12-byte encryption header, further - initializing the encryption keys. -3) Read and decrypt the compressed data stream using the - encryption keys. - -Step 1 - Initializing the encryption keys ------------------------------------------ - -Key(0) <- 305419896 -Key(1) <- 591751049 -Key(2) <- 878082192 - -loop for i <- 0 to length(password)-1 - update_keys(password(i)) -end loop - -Where update_keys() is defined as: - -update_keys(char): - Key(0) <- crc32(key(0),char) - Key(1) <- Key(1) + (Key(0) & 000000ffH) - Key(1) <- Key(1) * 134775813 + 1 - Key(2) <- crc32(key(2),key(1) >> 24) -end update_keys - -Where crc32(old_crc,char) is a routine that given a CRC value and a -character, returns an updated CRC value after applying the CRC-32 -algorithm described elsewhere in this document. - -Step 2 - Decrypting the encryption header ------------------------------------------ - -The purpose of this step is to further initialize the encryption -keys, based on random data, to render a plaintext attack on the -data ineffective. - -Read the 12-byte encryption header into Buffer, in locations -Buffer(0) thru Buffer(11). - -loop for i <- 0 to 11 - C <- buffer(i) ^ decrypt_byte() - update_keys(C) - buffer(i) <- C -end loop - -Where decrypt_byte() is defined as: - -unsigned char decrypt_byte() - local unsigned short temp - temp <- Key(2) | 2 - decrypt_byte <- (temp * (temp ^ 1)) >> 8 -end decrypt_byte - -After the header is decrypted, the last 1 or 2 bytes in Buffer -should be the high-order word/byte of the CRC for the file being -decrypted, stored in Intel low-byte/high-byte order. Versions of -PKZIP prior to 2.0 used a 2 byte CRC check; a 1 byte CRC check is -used on versions after 2.0. This can be used to test if the password -supplied is correct or not. - -Step 3 - Decrypting the compressed data stream ----------------------------------------------- - -The compressed data stream can be decrypted as follows: - -loop until done - read a character into C - Temp <- C ^ decrypt_byte() - update_keys(temp) - output Temp -end loop - - -XVI. Strong Encryption Specification ------------------------------------- - -The Strong Encryption technology defined in this specification is -covered under a pending patent application. The use or implementation -in a product of certain technological aspects set forth in the current -APPNOTE, including those with regard to strong encryption, patching, -or extended tape operations requires a license from PKWARE. Portions -of this Strong Encryption technology are available for use at no charge. -Contact PKWARE for licensing terms and conditions. Refer to section II -of this APPNOTE (Contacting PKWARE) for information on how to -contact PKWARE. - -Version 5.x of this specification introduced support for strong -encryption algorithms. These algorithms can be used with either -a password or an X.509v3 digital certificate to encrypt each file. -This format specification supports either password or certificate -based encryption to meet the security needs of today, to enable -interoperability between users within both PKI and non-PKI -environments, and to ensure interoperability between different -computing platforms that are running a ZIP program. - -Password based encryption is the most common form of encryption -people are familiar with. However, inherent weaknesses with -passwords (e.g. susceptibility to dictionary/brute force attack) -as well as password management and support issues make certificate -based encryption a more secure and scalable option. Industry -efforts and support are defining and moving towards more advanced -security solutions built around X.509v3 digital certificates and -Public Key Infrastructures(PKI) because of the greater scalability, -administrative options, and more robust security over traditional -password based encryption. - -Most standard encryption algorithms are supported with this -specification. Reference implementations for many of these -algorithms are available from either commercial or open source -distributors. Readily available cryptographic toolkits make -implementation of the encryption features straight-forward. -This document is not intended to provide a treatise on data -encryption principles or theory. Its purpose is to document the -data structures required for implementing interoperable data -encryption within the .ZIP format. It is strongly recommended that -you have a good understanding of data encryption before reading -further. - -The algorithms introduced in Version 5.0 of this specification -include: - - RC2 40 bit, 64 bit, and 128 bit - RC4 40 bit, 64 bit, and 128 bit - DES - 3DES 112 bit and 168 bit - -Version 5.1 adds support for the following: - - AES 128 bit, 192 bit, and 256 bit - - -Version 6.1 introduces encryption data changes to support -interoperability with Smartcard and USB Token certificate storage -methods which do not support the OAEP strengthening standard. - -Version 6.2 introduces support for encrypting metadata by compressing -and encrypting the central directory data structure to reduce information -leakage. Information leakage can occur in legacy ZIP applications -through exposure of information about a file even though that file is -stored encrypted. The information exposed consists of file -characteristics stored within the records and fields defined by this -specification. This includes data such as a files name, its original -size, timestamp and CRC32 value. - -Version 6.3 introduces support for encrypting data using the Blowfish -and Twofish algorithms. These are symmetric block ciphers developed -by Bruce Schneier. Blowfish supports using a variable length key from -32 to 448 bits. Block size is 64 bits. Implementations should use 16 -rounds and the only mode supported within ZIP files is CBC. Twofish -supports key sizes 128, 192 and 256 bits. Block size is 128 bits. -Implementations should use 16 rounds and the only mode supported within -ZIP files is CBC. Information and source code for both Blowfish and -Twofish algorithms can be found on the internet. Consult with the author -of these algorithms for information on terms or restrictions on use. - -Central Directory Encryption provides greater protection against -information leakage by encrypting the Central Directory structure and -by masking key values that are replicated in the unencrypted Local -Header. ZIP compatible programs that cannot interpret an encrypted -Central Directory structure cannot rely on the data in the corresponding -Local Header for decompression information. - -Extra Field records that may contain information about a file that should -not be exposed should not be stored in the Local Header and should only -be written to the Central Directory where they can be encrypted. This -design currently does not support streaming. Information in the End of -Central Directory record, the Zip64 End of Central Directory Locator, -and the Zip64 End of Central Directory records are not encrypted. Access -to view data on files within a ZIP file with an encrypted Central Directory -requires the appropriate password or private key for decryption prior to -viewing any files, or any information about the files, in the archive. - -Older ZIP compatible programs not familiar with the Central Directory -Encryption feature will no longer be able to recognize the Central -Directory and may assume the ZIP file is corrupt. Programs that -attempt streaming access using Local Headers will see invalid -information for each file. Central Directory Encryption need not be -used for every ZIP file. Its use is recommended for greater security. -ZIP files not using Central Directory Encryption should operate as -in the past. - -This strong encryption feature specification is intended to provide for -scalable, cross-platform encryption needs ranging from simple password -encryption to authenticated public/private key encryption. - -Encryption provides data confidentiality and privacy. It is -recommended that you combine X.509 digital signing with encryption -to add authentication and non-repudiation. - - -Single Password Symmetric Encryption Method: -------------------------------------------- - -The Single Password Symmetric Encryption Method using strong -encryption algorithms operates similarly to the traditional -PKWARE encryption defined in this format. Additional data -structures are added to support the processing needs of the -strong algorithms. - -The Strong Encryption data structures are: - -1. General Purpose Bits - Bits 0 and 6 of the General Purpose bit -flag in both local and central header records. Both bits set -indicates strong encryption. Bit 13, when set indicates the Central -Directory is encrypted and that selected fields in the Local Header -are masked to hide their actual value. - - -2. Extra Field 0x0017 in central header only. - - Fields to consider in this record are: - - Format - the data format identifier for this record. The only - value allowed at this time is the integer value 2. - - AlgId - integer identifier of the encryption algorithm from the - following range - - 0x6601 - DES - 0x6602 - RC2 (version needed to extract < 5.2) - 0x6603 - 3DES 168 - 0x6609 - 3DES 112 - 0x660E - AES 128 - 0x660F - AES 192 - 0x6610 - AES 256 - 0x6702 - RC2 (version needed to extract >= 5.2) - 0x6720 - Blowfish - 0x6721 - Twofish - 0x6801 - RC4 - 0xFFFF - Unknown algorithm - - Bitlen - Explicit bit length of key - - 32 - 448 bits - - Flags - Processing flags needed for decryption - - 0x0001 - Password is required to decrypt - 0x0002 - Certificates only - 0x0003 - Password or certificate required to decrypt - - Values > 0x0003 reserved for certificate processing - - -3. Decryption header record preceding compressed file data. - - -Decryption Header: - - Value Size Description - ----- ---- ----------- - IVSize 2 bytes Size of initialization vector (IV) - IVData IVSize Initialization vector for this file - Size 4 bytes Size of remaining decryption header data - Format 2 bytes Format definition for this record - AlgID 2 bytes Encryption algorithm identifier - Bitlen 2 bytes Bit length of encryption key - Flags 2 bytes Processing flags - ErdSize 2 bytes Size of Encrypted Random Data - ErdData ErdSize Encrypted Random Data - Reserved1 4 bytes Reserved certificate processing data - Reserved2 (var) Reserved for certificate processing data - VSize 2 bytes Size of password validation data - VData VSize-4 Password validation data - VCRC32 4 bytes Standard ZIP CRC32 of password validation data - - IVData - The size of the IV should match the algorithm block size. - The IVData can be completely random data. If the size of - the randomly generated data does not match the block size - it should be complemented with zero's or truncated as - necessary. If IVSize is 0,then IV = CRC32 + Uncompressed - File Size (as a 64 bit little-endian, unsigned integer value). - - Format - the data format identifier for this record. The only - value allowed at this time is the integer value 3. - - AlgId - integer identifier of the encryption algorithm from the - following range - - 0x6601 - DES - 0x6602 - RC2 (version needed to extract < 5.2) - 0x6603 - 3DES 168 - 0x6609 - 3DES 112 - 0x660E - AES 128 - 0x660F - AES 192 - 0x6610 - AES 256 - 0x6702 - RC2 (version needed to extract >= 5.2) - 0x6720 - Blowfish - 0x6721 - Twofish - 0x6801 - RC4 - 0xFFFF - Unknown algorithm - - Bitlen - Explicit bit length of key - - 32 - 448 bits - - Flags - Processing flags needed for decryption - - 0x0001 - Password is required to decrypt - 0x0002 - Certificates only - 0x0003 - Password or certificate required to decrypt - - Values > 0x0003 reserved for certificate processing - - ErdData - Encrypted random data is used to store random data that - is used to generate a file session key for encrypting - each file. SHA1 is used to calculate hash data used to - derive keys. File session keys are derived from a master - session key generated from the user-supplied password. - If the Flags field in the decryption header contains - the value 0x4000, then the ErdData field must be - decrypted using 3DES. If the value 0x4000 is not set, - then the ErdData field must be decrypted using AlgId. - - - Reserved1 - Reserved for certificate processing, if value is - zero, then Reserved2 data is absent. See the explanation - under the Certificate Processing Method for details on - this data structure. - - Reserved2 - If present, the size of the Reserved2 data structure - is located by skipping the first 4 bytes of this field - and using the next 2 bytes as the remaining size. See - the explanation under the Certificate Processing Method - for details on this data structure. - - VSize - This size value will always include the 4 bytes of the - VCRC32 data and will be greater than 4 bytes. - - VData - Random data for password validation. This data is VSize - in length and VSize must be a multiple of the encryption - block size. VCRC32 is a checksum value of VData. - VData and VCRC32 are stored encrypted and start the - stream of encrypted data for a file. - - -4. Useful Tips - -Strong Encryption is always applied to a file after compression. The -block oriented algorithms all operate in Cypher Block Chaining (CBC) -mode. The block size used for AES encryption is 16. All other block -algorithms use a block size of 8. Two ID's are defined for RC2 to -account for a discrepancy found in the implementation of the RC2 -algorithm in the cryptographic library on Windows XP SP1 and all -earlier versions of Windows. It is recommended that zero length files -not be encrypted, however programs should be prepared to extract them -if they are found within a ZIP file. - -A pseudo-code representation of the encryption process is as follows: - -Password = GetUserPassword() -MasterSessionKey = DeriveKey(SHA1(Password)) -RD = CryptographicStrengthRandomData() -For Each File - IV = CryptographicStrengthRandomData() - VData = CryptographicStrengthRandomData() - VCRC32 = CRC32(VData) - FileSessionKey = DeriveKey(SHA1(IV + RD) - ErdData = Encrypt(RD,MasterSessionKey,IV) - Encrypt(VData + VCRC32 + FileData, FileSessionKey,IV) -Done - -The function names and parameter requirements will depend on -the choice of the cryptographic toolkit selected. Almost any -toolkit supporting the reference implementations for each -algorithm can be used. The RSA BSAFE(r), OpenSSL, and Microsoft -CryptoAPI libraries are all known to work well. - - -Single Password - Central Directory Encryption: ------------------------------------------------ - -Central Directory Encryption is achieved within the .ZIP format by -encrypting the Central Directory structure. This encapsulates the metadata -most often used for processing .ZIP files. Additional metadata is stored for -redundancy in the Local Header for each file. The process of concealing -metadata by encrypting the Central Directory does not protect the data within -the Local Header. To avoid information leakage from the exposed metadata -in the Local Header, the fields containing information about a file are masked. - -Local Header: - -Masking replaces the true content of the fields for a file in the Local -Header with false information. When masked, the Local Header is not -suitable for streaming access and the options for data recovery of damaged -archives is reduced. Extra Data fields that may contain confidential -data should not be stored within the Local Header. The value set into -the Version needed to extract field should be the correct value needed to -extract the file without regard to Central Directory Encryption. The fields -within the Local Header targeted for masking when the Central Directory is -encrypted are: - - Field Name Mask Value - ------------------ --------------------------- - compression method 0 - last mod file time 0 - last mod file date 0 - crc-32 0 - compressed size 0 - uncompressed size 0 - file name (variable size) Base 16 value from the - range 1 - 0xFFFFFFFFFFFFFFFF - represented as a string whose - size will be set into the - file name length field - -The Base 16 value assigned as a masked file name is simply a sequentially -incremented value for each file starting with 1 for the first file. -Modifications to a ZIP file may cause different values to be stored for -each file. For compatibility, the file name field in the Local Header -should never be left blank. As of Version 6.2 of this specification, -the Compression Method and Compressed Size fields are not yet masked. -Fields having a value of 0xFFFF or 0xFFFFFFFF for the ZIP64 format -should not be masked. - -Encrypting the Central Directory: - -Encryption of the Central Directory does not include encryption of the -Central Directory Signature data, the Zip64 End of Central Directory -record, the Zip64 End of Central Directory Locator, or the End -of Central Directory record. The ZIP file comment data is never -encrypted. - -Before encrypting the Central Directory, it may optionally be compressed. -Compression is not required, but for storage efficiency it is assumed -this structure will be compressed before encrypting. Similarly, this -specification supports compressing the Central Directory without -requiring that it also be encrypted. Early implementations of this -feature will assume the encryption method applied to files matches the -encryption applied to the Central Directory. - -Encryption of the Central Directory is done in a manner similar to -that of file encryption. The encrypted data is preceded by a -decryption header. The decryption header is known as the Archive -Decryption Header. The fields of this record are identical to -the decryption header preceding each encrypted file. The location -of the Archive Decryption Header is determined by the value in the -Start of the Central Directory field in the Zip64 End of Central -Directory record. When the Central Directory is encrypted, the -Zip64 End of Central Directory record will always be present. - -The layout of the Zip64 End of Central Directory record for all -versions starting with 6.2 of this specification will follow the -Version 2 format. The Version 2 format is as follows: - -The leading fixed size fields within the Version 1 format for this -record remain unchanged. The record signature for both Version 1 -and Version 2 will be 0x06064b50. Immediately following the last -byte of the field known as the Offset of Start of Central -Directory With Respect to the Starting Disk Number will begin the -new fields defining Version 2 of this record. - -New fields for Version 2: - -Note: all fields stored in Intel low-byte/high-byte order. - - Value Size Description - ----- ---- ----------- - Compression Method 2 bytes Method used to compress the - Central Directory - Compressed Size 8 bytes Size of the compressed data - Original Size 8 bytes Original uncompressed size - AlgId 2 bytes Encryption algorithm ID - BitLen 2 bytes Encryption key length - Flags 2 bytes Encryption flags - HashID 2 bytes Hash algorithm identifier - Hash Length 2 bytes Length of hash data - Hash Data (variable) Hash data - -The Compression Method accepts the same range of values as the -corresponding field in the Central Header. - -The Compressed Size and Original Size values will not include the -data of the Central Directory Signature which is compressed or -encrypted. - -The AlgId, BitLen, and Flags fields accept the same range of values -the corresponding fields within the 0x0017 record. - -Hash ID identifies the algorithm used to hash the Central Directory -data. This data does not have to be hashed, in which case the -values for both the HashID and Hash Length will be 0. Possible -values for HashID are: - - Value Algorithm - ------ --------- - 0x0000 none - 0x0001 CRC32 - 0x8003 MD5 - 0x8004 SHA1 - 0x8007 RIPEMD160 - 0x800C SHA256 - 0x800D SHA384 - 0x800E SHA512 - -When the Central Directory data is signed, the same hash algorithm -used to hash the Central Directory for signing should be used. -This is recommended for processing efficiency, however, it is -permissible for any of the above algorithms to be used independent -of the signing process. - -The Hash Data will contain the hash data for the Central Directory. -The length of this data will vary depending on the algorithm used. - -The Version Needed to Extract should be set to 62. - -The value for the Total Number of Entries on the Current Disk will -be 0. These records will no longer support random access when -encrypting the Central Directory. - -When the Central Directory is compressed and/or encrypted, the -End of Central Directory record will store the value 0xFFFFFFFF -as the value for the Total Number of Entries in the Central -Directory. The value stored in the Total Number of Entries in -the Central Directory on this Disk field will be 0. The actual -values will be stored in the equivalent fields of the Zip64 -End of Central Directory record. - -Decrypting and decompressing the Central Directory is accomplished -in the same manner as decrypting and decompressing a file. - -Certificate Processing Method: ------------------------------ - -The Certificate Processing Method of for ZIP file encryption -defines the following additional data fields: - -1. Certificate Flag Values - -Additional processing flags that can be present in the Flags field of both -the 0x0017 field of the central directory Extra Field and the Decryption -header record preceding compressed file data are: - - 0x0007 - reserved for future use - 0x000F - reserved for future use - 0x0100 - Indicates non-OAEP key wrapping was used. If this - this field is set, the version needed to extract must - be at least 61. This means OAEP key wrapping is not - used when generating a Master Session Key using - ErdData. - 0x4000 - ErdData must be decrypted using 3DES-168, otherwise use the - same algorithm used for encrypting the file contents. - 0x8000 - reserved for future use - - -2. CertData - Extra Field 0x0017 record certificate data structure - -The data structure used to store certificate data within the section -of the Extra Field defined by the CertData field of the 0x0017 -record are as shown: - - Value Size Description - ----- ---- ----------- - RCount 4 bytes Number of recipients. - HashAlg 2 bytes Hash algorithm identifier - HSize 2 bytes Hash size - SRList (var) Simple list of recipients hashed public keys - - - RCount This defines the number intended recipients whose - public keys were used for encryption. This identifies - the number of elements in the SRList. - - HashAlg This defines the hash algorithm used to calculate - the public key hash of each public key used - for encryption. This field currently supports - only the following value for SHA-1 - - 0x8004 - SHA1 - - HSize This defines the size of a hashed public key. - - SRList This is a variable length list of the hashed - public keys for each intended recipient. Each - element in this list is HSize. The total size of - SRList is determined using RCount * HSize. - - -3. Reserved1 - Certificate Decryption Header Reserved1 Data: - - Value Size Description - ----- ---- ----------- - RCount 4 bytes Number of recipients. - - RCount This defines the number intended recipients whose - public keys were used for encryption. This defines - the number of elements in the REList field defined below. - - -4. Reserved2 - Certificate Decryption Header Reserved2 Data Structures: - - - Value Size Description - ----- ---- ----------- - HashAlg 2 bytes Hash algorithm identifier - HSize 2 bytes Hash size - REList (var) List of recipient data elements - - - HashAlg This defines the hash algorithm used to calculate - the public key hash of each public key used - for encryption. This field currently supports - only the following value for SHA-1 - - 0x8004 - SHA1 - - HSize This defines the size of a hashed public key - defined in REHData. - - REList This is a variable length of list of recipient data. - Each element in this list consists of a Recipient - Element data structure as follows: - - - Recipient Element (REList) Data Structure: - - Value Size Description - ----- ---- ----------- - RESize 2 bytes Size of REHData + REKData - REHData HSize Hash of recipients public key - REKData (var) Simple key blob - - - RESize This defines the size of an individual REList - element. This value is the combined size of the - REHData field + REKData field. REHData is defined by - HSize. REKData is variable and can be calculated - for each REList element using RESize and HSize. - - REHData Hashed public key for this recipient. - - REKData Simple Key Blob. The format of this data structure - is identical to that defined in the Microsoft - CryptoAPI and generated using the CryptExportKey() - function. The version of the Simple Key Blob - supported at this time is 0x02 as defined by - Microsoft. - -Certificate Processing - Central Directory Encryption: ------------------------------------------------------- - -Central Directory Encryption using Digital Certificates will -operate in a manner similar to that of Single Password Central -Directory Encryption. This record will only be present when there -is data to place into it. Currently, data is placed into this -record when digital certificates are used for either encrypting -or signing the files within a ZIP file. When only password -encryption is used with no certificate encryption or digital -signing, this record is not currently needed. When present, this -record will appear before the start of the actual Central Directory -data structure and will be located immediately after the Archive -Decryption Header if the Central Directory is encrypted. - -The Archive Extra Data record will be used to store the following -information. Additional data may be added in future versions. - -Extra Data Fields: - -0x0014 - PKCS#7 Store for X.509 Certificates -0x0016 - X.509 Certificate ID and Signature for central directory -0x0019 - PKCS#7 Encryption Recipient Certificate List - -The 0x0014 and 0x0016 Extra Data records that otherwise would be -located in the first record of the Central Directory for digital -certificate processing. When encrypting or compressing the Central -Directory, the 0x0014 and 0x0016 records must be located in the -Archive Extra Data record and they should not remain in the first -Central Directory record. The Archive Extra Data record will also -be used to store the 0x0019 data. - -When present, the size of the Archive Extra Data record will be -included in the size of the Central Directory. The data of the -Archive Extra Data record will also be compressed and encrypted -along with the Central Directory data structure. - -Certificate Processing Differences: - -The Certificate Processing Method of encryption differs from the -Single Password Symmetric Encryption Method as follows. Instead -of using a user-defined password to generate a master session key, -cryptographically random data is used. The key material is then -wrapped using standard key-wrapping techniques. This key material -is wrapped using the public key of each recipient that will need -to decrypt the file using their corresponding private key. - -This specification currently assumes digital certificates will follow -the X.509 V3 format for 1024 bit and higher RSA format digital -certificates. Implementation of this Certificate Processing Method -requires supporting logic for key access and management. This logic -is outside the scope of this specification. - -OAEP Processing with Certificate-based Encryption: - -OAEP stands for Optimal Asymmetric Encryption Padding. It is a -strengthening technique used for small encoded items such as decryption -keys. This is commonly applied in cryptographic key-wrapping techniques -and is supported by PKCS #1. Versions 5.0 and 6.0 of this specification -were designed to support OAEP key-wrapping for certificate-based -decryption keys for additional security. - -Support for private keys stored on Smartcards or Tokens introduced -a conflict with this OAEP logic. Most card and token products do -not support the additional strengthening applied to OAEP key-wrapped -data. In order to resolve this conflict, versions 6.1 and above of this -specification will no longer support OAEP when encrypting using -digital certificates. - -Versions of PKZIP available during initial development of the -certificate processing method set a value of 61 into the -version needed to extract field for a file. This indicates that -non-OAEP key wrapping is used. This affects certificate encryption -only, and password encryption functions should not be affected by -this value. This means values of 61 may be found on files encrypted -with certificates only, or on files encrypted with both password -encryption and certificate encryption. Files encrypted with both -methods can safely be decrypted using the password methods documented. - -XVII. Change Process --------------------- - -In order for the .ZIP file format to remain a viable definition, this -specification should be considered as open for periodic review and -revision. Although this format was originally designed with a -certain level of extensibility, not all changes in technology -(present or future) were or will be necessarily considered in its -design. If your application requires new definitions to the -extensible sections in this format, or if you would like to -submit new data structures, please forward your request to -zipformat@pkware.com. All submissions will be reviewed by the -ZIP File Specification Committee for possible inclusion into -future versions of this specification. Periodic revisions -to this specification will be published to ensure interoperability. -We encourage comments and feedback that may help improve clarity -or content. - -XVIII. Incorporating PKWARE Proprietary Technology into Your Product --------------------------------------------------------------------- - -PKWARE is committed to the interoperability and advancement of the -.ZIP format. PKWARE offers a free license for certain technological -aspects described above under certain restrictions and conditions. -However, the use or implementation in a product of certain technological -aspects set forth in the current APPNOTE, including those with regard to -strong encryption, patching, or extended tape operations requires a -license from PKWARE. Please contact PKWARE with regard to acquiring -a license. - -XIX. Acknowledgements ----------------------- - -In addition to the above mentioned contributors to PKZIP and PKUNZIP, -I would like to extend special thanks to Robert Mahoney for suggesting -the extension .ZIP for this software. - -XX. References --------------- - - Fiala, Edward R., and Greene, Daniel H., "Data compression with - finite windows", Communications of the ACM, Volume 32, Number 4, - April 1989, pages 490-505. - - Held, Gilbert, "Data Compression, Techniques and Applications, - Hardware and Software Considerations", John Wiley & Sons, 1987. - - Huffman, D.A., "A method for the construction of minimum-redundancy - codes", Proceedings of the IRE, Volume 40, Number 9, September 1952, - pages 1098-1101. - - Nelson, Mark, "LZW Data Compression", Dr. Dobbs Journal, Volume 14, - Number 10, October 1989, pages 29-37. - - Nelson, Mark, "The Data Compression Book", M&T Books, 1991. - - Storer, James A., "Data Compression, Methods and Theory", - Computer Science Press, 1988 - - Welch, Terry, "A Technique for High-Performance Data Compression", - IEEE Computer, Volume 17, Number 6, June 1984, pages 8-19. - - Ziv, J. and Lempel, A., "A universal algorithm for sequential data - compression", Communications of the ACM, Volume 30, Number 6, - June 1987, pages 520-540. - - Ziv, J. and Lempel, A., "Compression of individual sequences via - variable-rate coding", IEEE Transactions on Information Theory, - Volume 24, Number 5, September 1978, pages 530-536. - - -APPENDIX A - AS/400 Extra Field (0x0065) Attribute Definitions --------------------------------------------------------------- - -Field Definition Structure: - - a. field length including length 2 bytes - b. field code 2 bytes - c. data x bytes - -Field Code Description - 4001 Source type i.e. CLP etc - 4002 The text description of the library - 4003 The text description of the file - 4004 The text description of the member - 4005 x'F0' or 0 is PF-DTA, x'F1' or 1 is PF_SRC - 4007 Database Type Code 1 byte - 4008 Database file and fields definition - 4009 GZIP file type 2 bytes - 400B IFS code page 2 bytes - 400C IFS Creation Time 4 bytes - 400D IFS Access Time 4 bytes - 400E IFS Modification time 4 bytes - 005C Length of the records in the file 2 bytes - 0068 GZIP two words 8 bytes - -APPENDIX B - z/OS Extra Field (0x0065) Attribute Definitions ------------------------------------------------------------- - -Field Definition Structure: - - a. field length including length 2 bytes - b. field code 2 bytes - c. data x bytes - -Field Code Description - 0001 File Type 2 bytes - 0002 NonVSAM Record Format 1 byte - 0003 Reserved - 0004 NonVSAM Block Size 2 bytes Big Endian - 0005 Primary Space Allocation 3 bytes Big Endian - 0006 Secondary Space Allocation 3 bytes Big Endian - 0007 Space Allocation Type1 byte flag - 0008 Modification Date Retired with PKZIP 5.0 + - 0009 Expiration Date Retired with PKZIP 5.0 + - 000A PDS Directory Block Allocation 3 bytes Big Endian binary value - 000B NonVSAM Volume List variable - 000C UNIT Reference Retired with PKZIP 5.0 + - 000D DF/SMS Management Class 8 bytes EBCDIC Text Value - 000E DF/SMS Storage Class 8 bytes EBCDIC Text Value - 000F DF/SMS Data Class 8 bytes EBCDIC Text Value - 0010 PDS/PDSE Member Info. 30 bytes - 0011 VSAM sub-filetype 2 bytes - 0012 VSAM LRECL 13 bytes EBCDIC "(num_avg num_max)" - 0013 VSAM Cluster Name Retired with PKZIP 5.0 + - 0014 VSAM KSDS Key Information 13 bytes EBCDIC "(num_length num_position)" - 0015 VSAM Average LRECL 5 bytes EBCDIC num_value padded with blanks - 0016 VSAM Maximum LRECL 5 bytes EBCDIC num_value padded with blanks - 0017 VSAM KSDS Key Length 5 bytes EBCDIC num_value padded with blanks - 0018 VSAM KSDS Key Position 5 bytes EBCDIC num_value padded with blanks - 0019 VSAM Data Name 1-44 bytes EBCDIC text string - 001A VSAM KSDS Index Name 1-44 bytes EBCDIC text string - 001B VSAM Catalog Name 1-44 bytes EBCDIC text string - 001C VSAM Data Space Type 9 bytes EBCDIC text string - 001D VSAM Data Space Primary 9 bytes EBCDIC num_value left-justified - 001E VSAM Data Space Secondary 9 bytes EBCDIC num_value left-justified - 001F VSAM Data Volume List variable EBCDIC text list of 6-character Volume IDs - 0020 VSAM Data Buffer Space 8 bytes EBCDIC num_value left-justified - 0021 VSAM Data CISIZE 5 bytes EBCDIC num_value left-justified - 0022 VSAM Erase Flag 1 byte flag - 0023 VSAM Free CI % 3 bytes EBCDIC num_value left-justified - 0024 VSAM Free CA % 3 bytes EBCDIC num_value left-justified - 0025 VSAM Index Volume List variable EBCDIC text list of 6-character Volume IDs - 0026 VSAM Ordered Flag 1 byte flag - 0027 VSAM REUSE Flag 1 byte flag - 0028 VSAM SPANNED Flag 1 byte flag - 0029 VSAM Recovery Flag 1 byte flag - 002A VSAM WRITECHK Flag 1 byte flag - 002B VSAM Cluster/Data SHROPTS 3 bytes EBCDIC "n,y" - 002C VSAM Index SHROPTS 3 bytes EBCDIC "n,y" - 002D VSAM Index Space Type 9 bytes EBCDIC text string - 002E VSAM Index Space Primary 9 bytes EBCDIC num_value left-justified - 002F VSAM Index Space Secondary 9 bytes EBCDIC num_value left-justified - 0030 VSAM Index CISIZE 5 bytes EBCDIC num_value left-justified - 0031 VSAM Index IMBED 1 byte flag - 0032 VSAM Index Ordered Flag 1 byte flag - 0033 VSAM REPLICATE Flag 1 byte flag - 0034 VSAM Index REUSE Flag 1 byte flag - 0035 VSAM Index WRITECHK Flag 1 byte flag Retired with PKZIP 5.0 + - 0036 VSAM Owner 8 bytes EBCDIC text string - 0037 VSAM Index Owner 8 bytes EBCDIC text string - 0038 Reserved - 0039 Reserved - 003A Reserved - 003B Reserved - 003C Reserved - 003D Reserved - 003E Reserved - 003F Reserved - 0040 Reserved - 0041 Reserved - 0042 Reserved - 0043 Reserved - 0044 Reserved - 0045 Reserved - 0046 Reserved - 0047 Reserved - 0048 Reserved - 0049 Reserved - 004A Reserved - 004B Reserved - 004C Reserved - 004D Reserved - 004E Reserved - 004F Reserved - 0050 Reserved - 0051 Reserved - 0052 Reserved - 0053 Reserved - 0054 Reserved - 0055 Reserved - 0056 Reserved - 0057 Reserved - 0058 PDS/PDSE Member TTR Info. 6 bytes Big Endian - 0059 PDS 1st LMOD Text TTR 3 bytes Big Endian - 005A PDS LMOD EP Rec # 4 bytes Big Endian - 005B Reserved - 005C Max Length of records 2 bytes Big Endian - 005D PDSE Flag 1 byte flag - 005E Reserved - 005F Reserved - 0060 Reserved - 0061 Reserved - 0062 Reserved - 0063 Reserved - 0064 Reserved - 0065 Last Date Referenced 4 bytes Packed Hex "yyyymmdd" - 0066 Date Created 4 bytes Packed Hex "yyyymmdd" - 0068 GZIP two words 8 bytes - 0071 Extended NOTE Location 12 bytes Big Endian - 0072 Archive device UNIT 6 bytes EBCDIC - 0073 Archive 1st Volume 6 bytes EBCDIC - 0074 Archive 1st VOL File Seq# 2 bytes Binary - -APPENDIX C - Zip64 Extensible Data Sector Mappings (EFS) --------------------------------------------------------- - - -Z390 Extra Field: - - The following is the general layout of the attributes for the - ZIP 64 "extra" block for extended tape operations. Portions of - this extended tape processing technology is covered under a - pending patent application. The use or implementation in a - product of certain technological aspects set forth in the - current APPNOTE, including those with regard to strong encryption, - patching or extended tape operations, requires a license from - PKWARE. Please contact PKWARE with regard to acquiring a license. - - - Note: some fields stored in Big Endian format. All text is - in EBCDIC format unless otherwise specified. - - Value Size Description - ----- ---- ----------- - (Z390) 0x0065 2 bytes Tag for this "extra" block type - Size 4 bytes Size for the following data block - Tag 4 bytes EBCDIC "Z390" - Length71 2 bytes Big Endian - Subcode71 2 bytes Enote type code - FMEPos 1 byte - Length72 2 bytes Big Endian - Subcode72 2 bytes Unit type code - Unit 1 byte Unit - Length73 2 bytes Big Endian - Subcode73 2 bytes Volume1 type code - FirstVol 1 byte Volume - Length74 2 bytes Big Endian - Subcode74 2 bytes FirstVol file sequence - FileSeq 2 bytes Sequence - -APPENDIX D - Language Encoding (EFS) ------------------------------------- - -The ZIP format has historically supported only the original IBM PC character -encoding set, commonly referred to as IBM Code Page 437. This limits storing -file name characters to only those within the original MS-DOS range of values -and does not properly support file names in other character encodings, or -languages. To address this limitation, this specification will support the -following change. - -If general purpose bit 11 is unset, the file name and comment should conform -to the original ZIP character encoding. If general purpose bit 11 is set, the -filename and comment must support The Unicode Standard, Version 4.1.0 or -greater using the character encoding form defined by the UTF-8 storage -specification. The Unicode Standard is published by the The Unicode -Consortium (www.unicode.org). UTF-8 encoded data stored within ZIP files -is expected to not include a byte order mark (BOM). - -Applications may choose to supplement this file name storage through the use -of the 0x0008 Extra Field. Storage for this optional field is currently -undefined, however it will be used to allow storing extended information -on source or target encoding that may further assist applications with file -name, or file content encoding tasks. Please contact PKWARE with any -requirements on how this field should be used. - -The 0x0008 Extra Field storage may be used with either setting for general -purpose bit 11. Examples of the intended usage for this field is to store -whether "modified-UTF-8" (JAVA) is used, or UTF-8-MAC. Similarly, other -commonly used character encoding (code page) designations can be indicated -through this field. Formalized values for use of the 0x0008 record remain -undefined at this time. The definition for the layout of the 0x0008 field -will be published when available. Use of the 0x0008 Extra Field provides -for storing data within a ZIP file in an encoding other than IBM Code -Page 437 or UTF-8. - -General purpose bit 11 will not imply any encoding of file content or -password. Values defining character encoding for file content or -password must be stored within the 0x0008 Extended Language Encoding -Extra Field. - - |