From 058eba2d2171e38813d6ad722333ee58668d35b1 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Mon, 4 Sep 2023 15:40:05 -0400
Subject: sha3.[hc]: add sha3_{224,256,384,512}_{init,absorb,final}() and
 test_sha3_{224,256,384,512}_ctx()

---
 sha3.c | 662 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 sha3.h | 127 ++++++++++++-
 2 files changed, 787 insertions(+), 2 deletions(-)

diff --git a/sha3.c b/sha3.c
index 01dd4f8..4a7f512 100644
--- a/sha3.c
+++ b/sha3.c
@@ -213,6 +213,123 @@ void sha3_512(const uint8_t *m, size_t m_len, uint8_t dst[static 64]) {
   sha3(m, m_len, dst, 64);
 }
 
+// Initialize iterative sha3 hash context.
+static inline void sha3_init(sha3_t * const hash) {
+  memset(hash, 0, sizeof(sha3_t));
+}
+
+// Absorb input data into iterative SHA-3 hash context.
+static inline bool sha3_absorb(sha3_t * const hash, const size_t rate, const uint8_t * const src, const size_t len) {
+  if (hash->finalized) {
+    // hash already finalized, return false
+    return false;
+  }
+
+  // absorb bytes (FIXME: should absorb larger chunks)
+  for (size_t i = 0; i < len; i++) {
+    hash->a.u8[hash->num_bytes++] ^= src[i];
+    if (hash->num_bytes == rate) {
+      // permute
+      permute(hash->a.u64);
+      hash->num_bytes = 0;
+    }
+  }
+
+  // return success
+  return true;
+}
+
+// Finalize iterative SHA-3 hash context.
+static inline void sha3_final(sha3_t * const hash, const size_t rate, uint8_t * dst, const size_t dst_len) {
+  if (!hash->finalized) {
+    // mark context as final
+    hash->finalized = true;
+
+    // append suffix and padding
+    // (note: suffix and padding are ambiguous in spec)
+    hash->a.u8[hash->num_bytes] ^= 0x06;
+    hash->a.u8[rate - 1] ^= 0x80;
+
+    // permute
+    permute(hash->a.u64);
+  }
+
+  // copy to destination
+  memcpy(dst, hash->a.u8, dst_len);
+}
+
+#define SHA3_224_CAPACITY 28
+#define SHA3_224_RATE 200 - 2 * SHA3_224_CAPACITY
+
+// Initialize SHA3-224 iterative hash context.
+void sha3_224_init(sha3_t * const hash) {
+  sha3_init(hash);
+}
+
+// Absorb data into SHA3-224 iterative hash context.
+_Bool sha3_224_absorb(sha3_t * const hash, const uint8_t *src, const size_t len) {
+  return sha3_absorb(hash, SHA3_224_RATE, src, len);
+}
+
+// Finalize SHA3-224 iterative hash context.
+void sha3_224_final(sha3_t * const hash, uint8_t dst[SHA3_224_CAPACITY]) {
+  sha3_final(hash, SHA3_224_RATE, dst, SHA3_224_CAPACITY);
+}
+
+#define SHA3_256_CAPACITY 32
+#define SHA3_256_RATE 200 - 2 * SHA3_256_CAPACITY
+
+// Initialize SHA3-256 iterative hash context.
+void sha3_256_init(sha3_t * const hash) {
+  sha3_init(hash);
+}
+
+// Absorb data into SHA3-256 iterative hash context.
+_Bool sha3_256_absorb(sha3_t * const hash, const uint8_t *src, const size_t len) {
+  return sha3_absorb(hash, SHA3_256_RATE, src, len);
+}
+
+// Finalize SHA3-256 iterative hash context.
+void sha3_256_final(sha3_t * const hash, uint8_t dst[SHA3_256_CAPACITY]) {
+  sha3_final(hash, SHA3_256_RATE, dst, SHA3_256_CAPACITY);
+}
+
+#define SHA3_384_CAPACITY 48
+#define SHA3_384_RATE 200 - 2 * SHA3_384_CAPACITY
+
+// Initialize SHA3-384 iterative hash context.
+void sha3_384_init(sha3_t * const hash) {
+  sha3_init(hash);
+}
+
+// Absorb data into SHA3-384 iterative hash context.
+_Bool sha3_384_absorb(sha3_t * const hash, const uint8_t *src, const size_t len) {
+  return sha3_absorb(hash, SHA3_384_RATE, src, len);
+}
+
+// Finalize SHA3-384 iterative hash context.
+void sha3_384_final(sha3_t * const hash, uint8_t dst[SHA3_384_CAPACITY]) {
+  sha3_final(hash, SHA3_384_RATE, dst, SHA3_384_CAPACITY);
+}
+
+#define SHA3_512_CAPACITY 64
+#define SHA3_512_RATE 200 - 2 * SHA3_512_CAPACITY
+
+// Initialize SHA3-512 iterative hash context.
+void sha3_512_init(sha3_t * const hash) {
+  sha3_init(hash);
+}
+
+// Absorb data into SHA3-512 iterative hash context.
+_Bool sha3_512_absorb(sha3_t * const hash, const uint8_t *src, const size_t len) {
+  return sha3_absorb(hash, SHA3_512_RATE, src, len);
+}
+
+// Finalize SHA3-512 iterative hash context.
+void sha3_512_final(sha3_t * const hash, uint8_t dst[SHA3_512_CAPACITY]) {
+  sha3_final(hash, SHA3_512_RATE, dst, SHA3_512_CAPACITY);
+}
+
 static inline void shake(const uint8_t *m, size_t m_len, uint8_t * const dst, const size_t dst_len) {
   // in the sha3 xof functions, the capacity is always 2 times the
   // destination length, and the rate is the total state size minus the
@@ -2005,6 +2122,547 @@ static void test_sha3_512(void) {
   }
 }
 
+static void test_sha3_224_ctx(void) {
+  static const struct {
+    const char *name; // test name
+    const uint8_t msg[256]; // test message
+    const size_t len; // test message length
+    const uint8_t exp[28]; // expected hash
+  } tests[] = {{
+    .name = "empty",
+    .msg = "",
+    .len = 0,
+    .exp = {
+      0x6b, 0x4e, 0x03, 0x42, 0x36, 0x67, 0xdb, 0xb7,
+      0x3b, 0x6e, 0x15, 0x45, 0x4f, 0x0e, 0xb1, 0xab,
+      0xd4, 0x59, 0x7f, 0x9a, 0x1b, 0x07, 0x8e, 0x3f,
+      0x5b, 0x5a, 0x6b, 0xc7,
+    },
+  }, {
+    .name = "asdf",
+    .msg = "asdf",
+    .len = 4,
+    .exp = {
+      0x47, 0xcc, 0xa2, 0x03, 0xee, 0xfc, 0xa3, 0x49,
+      0xde, 0xaa, 0x41, 0x8d, 0xa7, 0xfe, 0x05, 0x38,
+      0x9e, 0xf6, 0x49, 0x98, 0x5c, 0x87, 0xa9, 0xb6,
+      0x55, 0xad, 0x12, 0x8c,
+    },
+  }, {
+    .name = "a-134",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 134,
+    .exp = {
+      0x5d, 0x1d, 0xb4, 0xe4, 0x7c, 0x0c, 0x4a, 0x42,
+      0x45, 0xb9, 0x0d, 0x18, 0x55, 0xb0, 0x7c, 0xb1,
+      0x6f, 0xb9, 0x40, 0xc5, 0x00, 0x76, 0xc1, 0xfd,
+      0x2a, 0xc2, 0x17, 0xfe,
+    },
+  }, {
+    .name = "a-135",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 135,
+    .exp = {
+      0xf9, 0xf2, 0x8c, 0x21, 0xa2, 0xb0, 0x88, 0x4b,
+      0xbd, 0x35, 0x94, 0xca, 0xe8, 0x2b, 0xf8, 0x11,
+      0xc0, 0xc1, 0xed, 0xe4, 0x27, 0xe0, 0x83, 0xd5,
+      0x57, 0x6e, 0x90, 0x9d,
+    },
+  }, {
+    .name = "a-136",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 136,
+    .exp = {
+      0x96, 0x13, 0x6a, 0x6a, 0x09, 0x44, 0x33, 0xb4,
+      0xaa, 0x85, 0x5f, 0x16, 0x38, 0x29, 0xa2, 0xce,
+      0x6b, 0xca, 0x7d, 0x56, 0xcf, 0xd2, 0x16, 0x3b,
+      0x47, 0xf1, 0xf1, 0xc4,
+    },
+  }, {
+    .name = "ff-256",
+    .msg = {
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    },
+    .len = 256,
+    .exp = {
+      0xb6, 0x53, 0x4d, 0x8b, 0xee, 0xdf, 0xb5, 0xed,
+      0x3f, 0x95, 0x3b, 0x09, 0xd1, 0x2f, 0xc3, 0x8f,
+      0x3d, 0x8b, 0x0b, 0xea, 0x9d, 0x80, 0xbd, 0x1e,
+      0x25, 0xc9, 0xfc, 0x35,
+    },
+  }, {
+    .name = "a-210",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 210,
+    .exp = {
+      0x03, 0x05, 0x4a, 0xb0, 0xa3, 0x37, 0x99, 0xbe,
+      0x2b, 0x17, 0xc8, 0x2b, 0x3a, 0x13, 0x90, 0x05,
+      0x2e, 0x49, 0xdf, 0x31, 0x6d, 0x85, 0x15, 0x2d,
+      0x74, 0x66, 0xab, 0x57,
+    },
+  }};
+
+  // run all tests
+  for (size_t i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+    // try all possible absorb sizes from 1 to len
+    for (size_t j = 1; j < tests[i].len; j++) {
+      // init
+      sha3_t hash;
+      sha3_224_init(&hash);
+
+      // absorb
+      for (size_t k = 0; k < tests[i].len; k += j) {
+        const size_t absorb_len = MIN(tests[i].len - k, j);
+        sha3_224_absorb(&hash, tests[i].msg + k, absorb_len);
+      }
+
+      // finalize
+      uint8_t got[28] = { 0 };
+      sha3_224_final(&hash, got);
+
+      // check
+      if (memcmp(got, tests[i].exp, sizeof(got))) {
+        fprintf(stderr, "test_sha3_224_ctx(\"%s\") failed, got:\n", tests[i].name);
+        dump_hex(stderr, got, 28);
+
+        fprintf(stderr, "exp:\n");
+        dump_hex(stderr, tests[i].exp, 28);
+      }
+    }
+  }
+}
+
+static void test_sha3_256_ctx(void) {
+  static const struct {
+    const char *name; // test name
+    const uint8_t msg[256]; // test message
+    const size_t len; // test message length
+    const uint8_t exp[32]; // expected hash
+  } tests[] = {{
+    .name = "empty",
+    .msg = "",
+    .len = 0,
+    .exp = {
+      0xa7, 0xff, 0xc6, 0xf8, 0xbf, 0x1e, 0xd7, 0x66,
+      0x51, 0xc1, 0x47, 0x56, 0xa0, 0x61, 0xd6, 0x62,
+      0xf5, 0x80, 0xff, 0x4d, 0xe4, 0x3b, 0x49, 0xfa,
+      0x82, 0xd8, 0x0a, 0x4b, 0x80, 0xf8, 0x43, 0x4a,
+    },
+  }, {
+    .name = "asdf",
+    .msg = "asdf",
+    .len = 4,
+    .exp = {
+      0xdd, 0x27, 0x81, 0xf4, 0xc5, 0x1b, 0xcc, 0xdb,
+      0xe2, 0x3e, 0x4d, 0x39, 0x8b, 0x8a, 0x82, 0x26,
+      0x1f, 0x58, 0x5c, 0x27, 0x8d, 0xbb, 0x4b, 0x84,
+      0x98, 0x9f, 0xea, 0x70, 0xe7, 0x67, 0x23, 0xa9,
+    },
+  }, {
+    .name = "a-134",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 134,
+    .exp = {
+      0x58, 0xb9, 0x70, 0xc3, 0x7a, 0xc2, 0xd6, 0x5b,
+      0x59, 0x9b, 0x69, 0x18, 0x68, 0xa6, 0x14, 0x01,
+      0xa5, 0x01, 0xc4, 0x0f, 0x23, 0x5d, 0x55, 0xf0,
+      0x59, 0xd3, 0x9a, 0x94, 0x2f, 0x41, 0xdc, 0xee,
+    },
+  }, {
+    .name = "a-135",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 135,
+    .exp = {
+      0x80, 0x94, 0xbb, 0x53, 0xc4, 0x4c, 0xfb, 0x1e,
+      0x67, 0xb7, 0xc3, 0x04, 0x47, 0xf9, 0xa1, 0xc3,
+      0x36, 0x96, 0xd2, 0x46, 0x3e, 0xcc, 0x1d, 0x9c,
+      0x92, 0x53, 0x89, 0x13, 0x39, 0x28, 0x43, 0xc9,
+    },
+  }, {
+    .name = "a-136",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 136,
+    .exp = {
+      0x3f, 0xc5, 0x55, 0x9f, 0x14, 0xdb, 0x8e, 0x45,
+      0x3a, 0x0a, 0x30, 0x91, 0xed, 0xbd, 0x2b, 0xc2,
+      0x5e, 0x11, 0x52, 0x8d, 0x81, 0xc6, 0x6f, 0xa5,
+      0x70, 0xa4, 0xef, 0xdc, 0xc2, 0x69, 0x5e, 0xe1,
+    },
+  }, {
+    .name = "ff-256",
+    .msg = {
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    },
+    .len = 256,
+    .exp = {
+      0xea, 0xa5, 0x7c, 0x69, 0x9a, 0x7a, 0x61, 0x4f,
+      0x9d, 0x96, 0x1e, 0x42, 0xd8, 0xb1, 0x2a, 0x93,
+      0x54, 0x6e, 0x8e, 0x80, 0xd3, 0x1f, 0x5c, 0xfc,
+      0xc4, 0x3f, 0x95, 0x39, 0xed, 0x06, 0x30, 0x7a,
+    },
+  }, {
+    .name = "a-210",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 210,
+    .exp = {
+      0xb4, 0x12, 0xbd, 0x70, 0xce, 0x67, 0xeb, 0x59,
+      0x0b, 0xb2, 0x25, 0x09, 0xef, 0x4e, 0x68, 0x7e,
+      0x02, 0xb4, 0x8e, 0x07, 0xd2, 0xbb, 0xd7, 0xbb,
+      0x9a, 0xfb, 0x58, 0x70, 0xfd, 0x14, 0xc1, 0x13,
+    },
+  }};
+
+  // run all tests
+  for (size_t i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+    // try all possible absorb sizes from 1 to len
+    for (size_t j = 1; j < tests[i].len; j++) {
+      // init context
+      sha3_t hash;
+      sha3_256_init(&hash);
+
+      // absorb
+      for (size_t k = 0; k < tests[i].len; k += j) {
+        const size_t absorb_len = MIN(tests[i].len - k, j);
+        sha3_256_absorb(&hash, tests[i].msg + k, absorb_len);
+      }
+
+      // finalize
+      uint8_t got[32] = { 0 };
+      sha3_256_final(&hash, got);
+
+      // check
+      if (memcmp(got, tests[i].exp, sizeof(got))) {
+        fprintf(stderr, "test_sha3_256_ctx(\"%s\") failed, got:\n", tests[i].name);
+        dump_hex(stderr, got, 32);
+
+        fprintf(stderr, "exp:\n");
+        dump_hex(stderr, tests[i].exp, 32);
+      }
+    }
+  }
+}
+
+static void test_sha3_384_ctx(void) {
+  static const struct {
+    const char *name; // test name
+    const uint8_t msg[256]; // test message
+    const size_t len; // test message length
+    const uint8_t exp[48]; // expected hash
+  } tests[] = {{
+    .name = "empty",
+    .msg = "",
+    .len = 0,
+    .exp = {
+      0x0c, 0x63, 0xa7, 0x5b, 0x84, 0x5e, 0x4f, 0x7d,
+      0x01, 0x10, 0x7d, 0x85, 0x2e, 0x4c, 0x24, 0x85,
+      0xc5, 0x1a, 0x50, 0xaa, 0xaa, 0x94, 0xfc, 0x61,
+      0x99, 0x5e, 0x71, 0xbb, 0xee, 0x98, 0x3a, 0x2a,
+      0xc3, 0x71, 0x38, 0x31, 0x26, 0x4a, 0xdb, 0x47,
+      0xfb, 0x6b, 0xd1, 0xe0, 0x58, 0xd5, 0xf0, 0x04,
+    },
+  }, {
+    .name = "asdf",
+    .msg = "asdf",
+    .len = 4,
+    .exp = {
+      0xcc, 0x8c, 0x24, 0x61, 0xa8, 0xac, 0xb5, 0x8c,
+      0x9e, 0x7b, 0x78, 0x95, 0x8e, 0xa3, 0x6d, 0x5f,
+      0xd3, 0x20, 0x38, 0xf9, 0x58, 0xcd, 0xbb, 0x59,
+      0xf2, 0x6b, 0x0f, 0xfd, 0x1c, 0x36, 0x57, 0x61,
+      0x83, 0xe1, 0xc2, 0xca, 0x33, 0x57, 0xca, 0x1e,
+      0x33, 0x3a, 0x11, 0xaf, 0xac, 0x8a, 0xed, 0xe6,
+    },
+  }, {
+    .name = "a-134",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 134,
+    .exp = {
+      0xac, 0x8b, 0xca, 0x5d, 0x14, 0xed, 0xb5, 0xfc,
+      0x82, 0xe2, 0x2e, 0x45, 0x33, 0x34, 0xcb, 0x39,
+      0xef, 0x43, 0x14, 0xa5, 0x9a, 0xd7, 0xba, 0x6f,
+      0xb1, 0x0f, 0x0b, 0x11, 0xbe, 0x7b, 0x4a, 0xf3,
+      0xfd, 0xe3, 0xe9, 0x54, 0x07, 0x81, 0xc2, 0x39,
+      0xfa, 0x4c, 0x1f, 0x60, 0x44, 0xf3, 0x1d, 0xa9,
+    },
+  }, {
+    .name = "a-135",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 135,
+    .exp = {
+      0xa2, 0xd5, 0x19, 0x07, 0xc0, 0x61, 0x1e, 0x25,
+      0xc0, 0x58, 0xf0, 0x67, 0x50, 0x42, 0xe8, 0xf5,
+      0x3c, 0xc4, 0x73, 0xdc, 0x34, 0x7c, 0x5e, 0xa8,
+      0xa8, 0x13, 0xd8, 0x86, 0xb3, 0xaa, 0x8f, 0x8d,
+      0xca, 0xb6, 0x1a, 0x23, 0x62, 0x37, 0xd9, 0x4d,
+      0xe4, 0x04, 0xcd, 0x66, 0x60, 0x62, 0x43, 0xf9,
+    },
+  }, {
+    .name = "a-136",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 136,
+    .exp = {
+      0xcb, 0xbc, 0xb4, 0x66, 0x41, 0x7a, 0x2f, 0x6d,
+      0x46, 0x64, 0x79, 0xbb, 0x6d, 0xc6, 0x59, 0x43,
+      0x4d, 0x95, 0x89, 0xde, 0x3a, 0x53, 0xac, 0xc9,
+      0xb4, 0x27, 0x58, 0x04, 0x82, 0xe3, 0x05, 0x94,
+      0x88, 0x88, 0xc8, 0xfa, 0x6d, 0x06, 0x9c, 0x5e,
+      0x6a, 0x89, 0x9a, 0xa3, 0x4a, 0x9a, 0xf1, 0x5a,
+    },
+  }, {
+    .name = "ff-256",
+    .msg = {
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    },
+    .len = 256,
+    .exp = {
+      0x91, 0xb2, 0xc0, 0xab, 0x2c, 0xe3, 0x31, 0xcd,
+      0x59, 0xab, 0x98, 0x3b, 0x87, 0xaf, 0xc9, 0xe5,
+      0x45, 0x66, 0x33, 0xb1, 0x30, 0x49, 0xac, 0x84,
+      0x36, 0x04, 0xc9, 0xb6, 0xc3, 0xab, 0x09, 0xc3,
+      0x5c, 0xf8, 0x8c, 0xcb, 0xf7, 0x61, 0xc5, 0x64,
+      0x7c, 0x92, 0x2b, 0xcc, 0x9b, 0x37, 0x5a, 0x6b,
+    },
+  }, {
+    .name = "a-210",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 210,
+    .exp = {
+      0x23, 0x2f, 0xba, 0x5c, 0x81, 0x59, 0x36, 0xc7,
+      0x7b, 0x37, 0x3a, 0x5e, 0x5d, 0xa0, 0xd2, 0xca,
+      0x3b, 0x15, 0xcd, 0x28, 0x58, 0x92, 0x66, 0x14,
+      0x5a, 0x92, 0xd6, 0x50, 0xfa, 0x58, 0xef, 0x4f,
+      0xdf, 0xa3, 0x4e, 0x9e, 0x2f, 0x0e, 0xa8, 0x7a,
+      0x67, 0x32, 0x8f, 0x68, 0x9a, 0x6b, 0x8f, 0x04,
+    },
+  }};
+
+  // run all tests
+  for (size_t i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+    // try all possible absorb sizes from 1 to len
+    for (size_t j = 1; j < tests[i].len; j++) {
+      // init
+      sha3_t hash;
+      sha3_384_init(&hash);
+
+      // absorb
+      for (size_t k = 0; k < tests[i].len; k += j) {
+        const size_t absorb_len = MIN(tests[i].len - k, j);
+        sha3_384_absorb(&hash, tests[i].msg + k, absorb_len);
+      }
+
+      // finalize
+      uint8_t got[48] = { 0 };
+      sha3_384_final(&hash, got);
+
+      // check
+      if (memcmp(got, tests[i].exp, sizeof(got))) {
+        fprintf(stderr, "test_sha3_384_ctx(\"%s\") failed, got:\n", tests[i].name);
+        dump_hex(stderr, got, 48);
+
+        fprintf(stderr, "exp:\n");
+        dump_hex(stderr, tests[i].exp, 48);
+      }
+    }
+  }
+}
+
+static void test_sha3_512_ctx(void) {
+  static const struct {
+    const char *name; // test name
+    const uint8_t msg[256]; // test message
+    const size_t len; // test message length
+    const uint8_t exp[64]; // expected hash
+  } tests[] = {{
+    .name = "empty",
+    .msg = "",
+    .len = 0,
+    .exp = {
+      0xa6, 0x9f, 0x73, 0xcc, 0xa2, 0x3a, 0x9a, 0xc5,
+      0xc8, 0xb5, 0x67, 0xdc, 0x18, 0x5a, 0x75, 0x6e,
+      0x97, 0xc9, 0x82, 0x16, 0x4f, 0xe2, 0x58, 0x59,
+      0xe0, 0xd1, 0xdc, 0xc1, 0x47, 0x5c, 0x80, 0xa6,
+      0x15, 0xb2, 0x12, 0x3a, 0xf1, 0xf5, 0xf9, 0x4c,
+      0x11, 0xe3, 0xe9, 0x40, 0x2c, 0x3a, 0xc5, 0x58,
+      0xf5, 0x00, 0x19, 0x9d, 0x95, 0xb6, 0xd3, 0xe3,
+      0x01, 0x75, 0x85, 0x86, 0x28, 0x1d, 0xcd, 0x26,
+    },
+  }, {
+    .name = "asdf",
+    .msg = "asdf",
+    .len = 4,
+    .exp = {
+      0x8d, 0x88, 0xcf, 0x5b, 0x20, 0xf5, 0x3a, 0xcd,
+      0x7a, 0xe1, 0x47, 0x9b, 0x5b, 0x36, 0xdc, 0x20,
+      0x21, 0x75, 0x3b, 0x04, 0x99, 0x02, 0xc7, 0x72,
+      0x47, 0xbb, 0x27, 0xb1, 0x31, 0xb3, 0x00, 0xbd,
+      0x3c, 0xa8, 0xbe, 0xef, 0x28, 0x75, 0x6d, 0xce,
+      0x27, 0xb8, 0x99, 0x08, 0x67, 0xc4, 0x57, 0x7a,
+      0x25, 0x35, 0xe7, 0xe3, 0xb7, 0x51, 0x41, 0x39,
+      0x9c, 0xa1, 0xa9, 0x4c, 0xc8, 0x4b, 0x0e, 0xb9,
+    },
+  }, {
+    .name = "a-134",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 134,
+    .exp = {
+      0x4e, 0x72, 0xa4, 0xf6, 0x55, 0x99, 0xa2, 0x47,
+      0x2a, 0x66, 0xf8, 0xa8, 0xd6, 0xcf, 0xb3, 0x84,
+      0xb7, 0xd3, 0x4f, 0x52, 0xec, 0xaa, 0x00, 0xe9,
+      0xf0, 0x66, 0x82, 0x0b, 0x0e, 0xdc, 0x1f, 0xcc,
+      0x9c, 0xf3, 0x12, 0x0b, 0x81, 0x46, 0x89, 0xbc,
+      0x62, 0xb7, 0x72, 0x0f, 0x4e, 0x4c, 0x99, 0x3d,
+      0xa0, 0x84, 0x08, 0x27, 0xf6, 0x95, 0x03, 0x8a,
+      0x82, 0x18, 0x69, 0xe8, 0xa6, 0x27, 0x60, 0xe8,
+    },
+  }, {
+    .name = "a-135",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 135,
+    .exp = {
+      0x4b, 0xe1, 0xe7, 0x02, 0x76, 0xf9, 0x12, 0x2f,
+      0x47, 0x0a, 0x54, 0xc2, 0x72, 0x40, 0xc7, 0xd0,
+      0x70, 0x9d, 0xab, 0x74, 0x69, 0x95, 0x8b, 0x48,
+      0xa9, 0x50, 0xd6, 0x9d, 0xa6, 0xdd, 0x07, 0xca,
+      0x13, 0x58, 0x26, 0xd9, 0xd2, 0x3e, 0x97, 0x5c,
+      0xb9, 0x28, 0x3e, 0x7d, 0x23, 0x6e, 0xf9, 0x8a,
+      0x80, 0x45, 0x1d, 0xca, 0x8e, 0x31, 0x1f, 0x52,
+      0x09, 0x63, 0x08, 0xb2, 0xc8, 0xd7, 0x0c, 0xc7,
+    },
+  }, {
+    .name = "a-136",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 136,
+    .exp = {
+      0xe5, 0x03, 0x92, 0xc9, 0x1e, 0xd9, 0x57, 0x68,
+      0xc8, 0xdc, 0xf5, 0x2a, 0x12, 0xe5, 0xdb, 0x1e,
+      0xcd, 0x03, 0x47, 0xfb, 0x99, 0x5f, 0x7f, 0xf4,
+      0xea, 0x06, 0x99, 0x46, 0x49, 0xbb, 0xd1, 0xa0,
+      0xde, 0x7a, 0xe3, 0x6a, 0x62, 0xaa, 0xdc, 0x00,
+      0xa7, 0x04, 0xd7, 0x30, 0xb5, 0x2b, 0xda, 0x19,
+      0x1b, 0x72, 0x95, 0x1e, 0x2a, 0xfc, 0x9b, 0x6f,
+      0xb6, 0x82, 0x47, 0x87, 0xb2, 0x08, 0x62, 0x57,
+    },
+  }, {
+    .name = "ff-256",
+    .msg = {
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    },
+    .len = 256,
+    .exp = {
+      0x02, 0x3a, 0x91, 0x27, 0xcf, 0x29, 0x6d, 0x01,
+      0x12, 0x0e, 0x3d, 0xaa, 0x92, 0x76, 0x15, 0x23,
+      0x8e, 0x97, 0xdd, 0xb6, 0x33, 0x26, 0xe2, 0x89,
+      0xb3, 0x31, 0xe2, 0x25, 0xbe, 0x41, 0xea, 0xd5,
+      0x90, 0xf1, 0xdd, 0x5c, 0x80, 0x1d, 0x91, 0x03,
+      0xfe, 0x65, 0x7d, 0x23, 0x63, 0xbd, 0xb2, 0x66,
+      0xe7, 0x90, 0xb1, 0x89, 0x0b, 0x3d, 0xd5, 0x79,
+      0xdc, 0xa7, 0xf9, 0x1f, 0x5f, 0x4d, 0x98, 0x49,
+    },
+  }, {
+    .name = "a-210",
+    .msg = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    .len = 210,
+    .exp = {
+      0x47, 0xfa, 0xd7, 0x8d, 0x72, 0x35, 0xe5, 0xcd,
+      0xb9, 0xd7, 0x23, 0x6c, 0xfc, 0xf2, 0x79, 0xdb,
+      0x0f, 0x8a, 0xcd, 0x5b, 0xf1, 0x7b, 0xdc, 0x74,
+      0x18, 0xe4, 0x29, 0xb7, 0x1a, 0x0a, 0x21, 0xb7,
+      0xed, 0xe8, 0x54, 0x64, 0xcf, 0x69, 0x44, 0x63,
+      0xff, 0x0e, 0x56, 0xf2, 0x8f, 0x04, 0xbf, 0x85,
+      0xc0, 0x85, 0xe1, 0x17, 0x6a, 0x47, 0xd7, 0x3b,
+      0xf2, 0x8b, 0xdb, 0xa0, 0x4f, 0x4a, 0xe7, 0x61,
+    },
+  }};
+
+  for (size_t i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+    // try all possible absorb sizes from 1 to len
+    for (size_t j = 1; j < tests[i].len; j++) {
+      // init
+      sha3_t hash;
+      sha3_512_init(&hash);
+
+      // absorb
+      for (size_t k = 0; k < tests[i].len; k += j) {
+        const size_t absorb_len = MIN(tests[i].len - k, j);
+        sha3_512_absorb(&hash, tests[i].msg + k, absorb_len);
+      }
+
+      // finalize
+      uint8_t got[64] = { 0 };
+      sha3_512_final(&hash, got);
+
+      // check
+      if (memcmp(got, tests[i].exp, sizeof(got))) {
+        fprintf(stderr, "test_sha3_512_ctx(\"%s\") failed, got:\n", tests[i].name);
+        dump_hex(stderr, got, 64);
+
+        fprintf(stderr, "exp:\n");
+        dump_hex(stderr, tests[i].exp, 64);
+      }
+    }
+  }
+}
+
 static void test_shake128(void) {
   static const struct {
     const char *name; // test name
@@ -4238,6 +4896,10 @@ int main(void) {
   test_sha3_256();
   test_sha3_384();
   test_sha3_512();
+  test_sha3_224_ctx();
+  test_sha3_256_ctx();
+  test_sha3_384_ctx();
+  test_sha3_512_ctx();
   test_shake128();
   test_shake256();
   test_shake128_xof();
diff --git a/sha3.h b/sha3.h
index 9e2a015..003d5b5 100644
--- a/sha3.h
+++ b/sha3.h
@@ -11,13 +11,20 @@ extern "C" {
 
 #include <stdint.h>
 
-// sha3 state
+// Internal sha3 state.
 typedef union {
   uint8_t u8[200];
   uint64_t u64[25];
 } sha3_state_t;
 
-// Internal XOF state
+// Iterative SHA-3 context (all members are private).
+typedef struct {
+  size_t num_bytes; // number of bytes absorbed
+  sha3_state_t a; // internal state
+  _Bool finalized; // mode (absorbing or finalized)
+} sha3_t;
+
+// Iterative XOF context (all members are private).
 typedef struct {
   size_t num_bytes; // number of bytes absorbed
   sha3_state_t a; // internal state
@@ -35,6 +42,35 @@ typedef struct {
  */
 void sha3_224(const uint8_t *m, size_t m_len, uint8_t dst[static 28]);
 
+/**
+ * Initialize SHA3-224 hash context.
+ *
+ * @param[out] hash SHA3-224 hash context.
+ */
+void sha3_224_init(sha3_t *hash);
+
+/**
+ * Absorb input data in `src` of length `len` bytes into SHA3-224 hash
+ * context `hash`.  Can be called iteratively to absorb input data in
+ * chunks.
+ *
+ * @param[in/out] hash SHA3-224 hash context.
+ * @param[in] src Input data.
+ * @param[in] len Input data length, in bytes.
+ *
+ * @return True if data was absorbed, and false otherwise (e.g., if context has already been finalized).
+ */
+_Bool sha3_224_absorb(sha3_t *hash, const uint8_t *src, const size_t len);
+
+/**
+ * Finalize SHA3-224 hash context and write 28 bytes of output to
+ * destination buffer `dst`.
+ *
+ * @param[in/out] hash SHA3-224 hash context.
+ * @param[out] dst Destination buffer.  Must be at least 28 bytes in length.
+ */
+void sha3_224_final(sha3_t *hash, uint8_t dst[28]);
+
 /**
  * Hash input message in input buffer `m` of length `m_len` bytes with
  * SHA3-256 (FIPS 202, section 6.1) and write 32 bytes of output to
@@ -46,6 +82,35 @@ void sha3_224(const uint8_t *m, size_t m_len, uint8_t dst[static 28]);
  */
 void sha3_256(const uint8_t *m, size_t m_len, uint8_t dst[static 32]);
 
+/**
+ * Initialize SHA3-256 hash context.
+ *
+ * @param[out] hash SHA3-256 hash context.
+ */
+void sha3_256_init(sha3_t *hash);
+
+/**
+ * Absorb input data in `src` of length `len` bytes into SHA3-256 hash
+ * context `hash`.  Can be called iteratively to absorb input data in
+ * chunks.
+ *
+ * @param[in/out] hash SHA3-256 hash context.
+ * @param[in] src Input data.
+ * @param[in] len Input data length, in bytes.
+ *
+ * @return True if data was absorbed, and false otherwise (e.g., if context has already been finalized).
+ */
+_Bool sha3_256_absorb(sha3_t *hash, const uint8_t *src, const size_t len);
+
+/**
+ * Finalize SHA3-256 hash context and write 28 bytes of output to
+ * destination buffer `dst`.
+ *
+ * @param[in/out] hash SHA3-256 hash context.
+ * @param[out] dst Destination buffer.  Must be at least 32 bytes in length.
+ */
+void sha3_256_final(sha3_t *hash, uint8_t dst[32]);
+
 /**
  * Hash input message in input buffer `m` of length `m_len` bytes with
  * SHA3-384 (FIPS 202, section 6.1) and write 48 bytes of output to
@@ -57,6 +122,35 @@ void sha3_256(const uint8_t *m, size_t m_len, uint8_t dst[static 32]);
  */
 void sha3_384(const uint8_t *m, size_t m_len, uint8_t dst[static 48]);
 
+/**
+ * Initialize SHA3-384 hash context.
+ *
+ * @param[out] hash SHA3-384 hash context.
+ */
+void sha3_384_init(sha3_t *hash);
+
+/**
+ * Absorb input data in `src` of length `len` bytes into SHA3-384 hash
+ * context `hash`.  Can be called iteratively to absorb input data in
+ * chunks.
+ *
+ * @param[in/out] hash SHA3-384 hash context.
+ * @param[in] src Input data.
+ * @param[in] len Input data length, in bytes.
+ *
+ * @return True if data was absorbed, and false otherwise (e.g., if context has already been finalized).
+ */
+_Bool sha3_384_absorb(sha3_t *hash, const uint8_t *src, const size_t len);
+
+/**
+ * Finalize SHA3-384 hash context and write 28 bytes of output to
+ * destination buffer `dst`.
+ *
+ * @param[in/out] hash SHA3-384 hash context.
+ * @param[out] dst Destination buffer.  Must be at least 48 bytes in length.
+ */
+void sha3_384_final(sha3_t *hash, uint8_t dst[48]);
+
 /**
  * Hash input message in input buffer `m` of length `m_len` bytes with
  * SHA3-512 (FIPS 202, section 6.1) and write 64 bytes of output to
@@ -68,6 +162,35 @@ void sha3_384(const uint8_t *m, size_t m_len, uint8_t dst[static 48]);
  */
 void sha3_512(const uint8_t *m, size_t m_len, uint8_t dst[static 64]);
 
+/**
+ * Initialize SHA3-512 hash context.
+ *
+ * @param[out] hash SHA3-512 hash context.
+ */
+void sha3_512_init(sha3_t *hash);
+
+/**
+ * Absorb input data in `src` of length `len` bytes into SHA3-512 hash
+ * context `hash`.  Can be called iteratively to absorb input data in
+ * chunks.
+ *
+ * @param[in/out] hash SHA3-512 hash context.
+ * @param[in] src Input data.
+ * @param[in] len Input data length, in bytes.
+ *
+ * @return True if data was absorbed, and false otherwise (e.g., if context has already been finalized).
+ */
+_Bool sha3_512_absorb(sha3_t *hash, const uint8_t *src, const size_t len);
+
+/**
+ * Finalize SHA3-512 hash context and write 28 bytes of output to
+ * destination buffer `dst`.
+ *
+ * @param[in/out] hash SHA3-512 hash context.
+ * @param[out] dst Destination buffer.  Must be at least 64 bytes in length.
+ */
+void sha3_512_final(sha3_t *hash, uint8_t dst[64]);
+
 /**
  * Hash input message in buffer `m` of length `m_len` bytes with
  * SHAKE128 (FIPS 202, section 6.2) and write 16 bytes of output to
-- 
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