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authorPaul Duncan <pabs@pablotron.org>2023-09-03 00:16:53 -0400
committerPaul Duncan <pabs@pablotron.org>2023-09-03 00:16:53 -0400
commit1c86d0225c1e1fd76e92c640594ab6ce38161c85 (patch)
treee6c451f0a8efe8a37f336242bf057d1a89f0104d
parent9e3d518710945923681e0babc632200a7d82a122 (diff)
downloadsha3-1c86d0225c1e1fd76e92c640594ab6ce38161c85.tar.bz2
sha3-1c86d0225c1e1fd76e92c640594ab6ce38161c85.zip
sha3.c: add right_encode()
-rw-r--r--sha3.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/sha3.c b/sha3.c
index fe9e55d..cc4a367 100644
--- a/sha3.c
+++ b/sha3.c
@@ -408,6 +408,70 @@ static inline size_t left_encode(uint8_t buf[static 9], const uint64_t n) {
}
}
+// NIST SP 800-105 utility function.
+static inline size_t right_encode(uint8_t buf[static 9], const uint64_t n) {
+ if (n > 0x00ffffffffffffffULL) {
+ buf[0] = (n >> 56) & 0xff;
+ buf[1] = (n >> 40) & 0xff;
+ buf[2] = (n >> 32) & 0xff;
+ buf[3] = (n >> 24) & 0xff;
+ buf[4] = (n >> 16) & 0xff;
+ buf[5] = (n >> 8) & 0xff;
+ buf[6] = n & 0xff;
+ buf[7] = 8;
+ return 9;
+ } else if (n > 0x0000ffffffffffffULL) {
+ buf[0] = (n >> 56) & 0xff;
+ buf[1] = (n >> 40) & 0xff;
+ buf[2] = (n >> 32) & 0xff;
+ buf[3] = (n >> 24) & 0xff;
+ buf[4] = (n >> 16) & 0xff;
+ buf[5] = (n >> 8) & 0xff;
+ buf[6] = n & 0xff;
+ buf[7] = 7;
+ return 8;
+ } else if (n > 0x000000ffffffffffULL) {
+ buf[0] = (n >> 40) & 0xff;
+ buf[1] = (n >> 32) & 0xff;
+ buf[2] = (n >> 24) & 0xff;
+ buf[3] = (n >> 16) & 0xff;
+ buf[4] = (n >> 8) & 0xff;
+ buf[5] = n & 0xff;
+ buf[6] = 6;
+ return 7;
+ } else if (n > 0x00000000ffffffffULL) {
+ buf[0] = (n >> 32) & 0xff;
+ buf[1] = (n >> 24) & 0xff;
+ buf[2] = (n >> 16) & 0xff;
+ buf[3] = (n >> 8) & 0xff;
+ buf[4] = n & 0xff;
+ buf[5] = 5;
+ return 6;
+ } else if (n > 0x0000000000ffffffULL) {
+ buf[0] = (n >> 24) & 0xff;
+ buf[1] = (n >> 16) & 0xff;
+ buf[2] = (n >> 8) & 0xff;
+ buf[3] = n & 0xff;
+ buf[4] = 4;
+ return 5;
+ } else if (n > 0x000000000000ffffULL) {
+ buf[0] = (n >> 16) & 0xff;
+ buf[1] = (n >> 8) & 0xff;
+ buf[2] = n & 0xff;
+ buf[3] = 3;
+ return 4;
+ } else if (n > 0x00000000000000ffULL) {
+ buf[0] = (n >> 8) & 0xff;
+ buf[1] = n & 0xff;
+ buf[2] = 2;
+ return 3;
+ } else {
+ buf[0] = n & 0xff;
+ buf[1] = 1;
+ return 2;
+ }
+}
+
// Write prefix for encode_string() to the given buffer. Accepts the
// length of the string, in bytes.
//
@@ -2028,6 +2092,76 @@ static void test_left_encode(void) {
}
}
+static void test_right_encode(void) {
+ static const struct {
+ const char *name;
+ uint64_t val;
+ uint8_t exp[9];
+ size_t exp_len;
+ } tests[] = {{
+ .name = "zero",
+ .val = 0,
+ .exp = { 0x00, 0x01 },
+ .exp_len = 2,
+ }, {
+ .name = "120",
+ .val = 120,
+ .exp = { 0x78, 0x01 },
+ .exp_len = 2,
+ }, {
+ .name = "256",
+ .val = 256,
+ .exp = { 0x01, 0x00, 0x02 },
+ .exp_len = 3,
+ }, {
+ .name = "65535",
+ .val = 65535,
+ .exp = { 0xff, 0xff, 0x02 },
+ .exp_len = 3,
+ }, {
+ .name = "65536",
+ .val = 65536,
+ .exp = { 0x01, 0x00, 0x00, 0x03 },
+ .exp_len = 4,
+ }, {
+ .name = "0xff00ff",
+ .val = 0xff00ff,
+ .exp = { 0xff, 0x00, 0xff, 0x03 },
+ .exp_len = 4,
+ }, {
+ .name = "0x01000000",
+ .val = 0x01000000,
+ .exp = { 0x01, 0x00, 0x00, 0x00, 0x04 },
+ .exp_len = 5,
+ }, {
+ .name = "0xffffffff",
+ .val = 0xffffffff,
+ .exp = { 0xff, 0xff, 0xff, 0xff, 0x04 },
+ .exp_len = 5,
+ }, {
+ .name = "0x0100000000",
+ .val = 0x0100000000,
+ .exp = { 0x01, 0x00, 0x00, 0x00, 0x00, 0x05 },
+ .exp_len = 6,
+ }};
+
+ for (size_t i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+ uint8_t got[9];
+ const size_t got_len = right_encode(got, tests[i].val);
+
+ // check length and data
+ if (got_len != tests[i].exp_len) {
+ fprintf(stderr, "test_right_encode(\"%s\") length check failed: got %zu, exp %zu:\n", tests[i].name, got_len, tests[i].exp_len);
+ } else if (memcmp(got, tests[i].exp, got_len)) {
+ fprintf(stderr, "test_right_encode(\"%s\") failed, got:\n", tests[i].name);
+ dump_hex(stderr, got, got_len);
+
+ fprintf(stderr, "exp:\n");
+ dump_hex(stderr, tests[i].exp, got_len);
+ }
+ }
+}
+
static void test_encode_string_prefix(void) {
static const struct {
const char *name;
@@ -2315,6 +2449,7 @@ int main(void) {
test_shake256_xof();
test_shake256_xof_once();
test_left_encode();
+ test_right_encode();
test_encode_string_prefix();
test_bytepad_prefix();
test_cshake128();