text: /* LibTomCrypt, modular cryptographic library -- Tom St Denis
   *
   * LibTomCrypt is a library that provides various cryptographic
   * algorithms in a highly modular and flexible manner.
   *
   * The library is free for all purposes without any express
   * guarantee it works.
   */
  
  /* based on https://github.com/brainhub/SHA3IUF (public domain) */
  
  #include "tomcrypt.h"
  
  #ifdef LTC_SHA3
  
  const struct ltc_hash_descriptor sha3_224_desc =
  {
     "sha3-224",                  /* name of hash */
     17,                          /* internal ID */
     28,                          /* Size of digest in octets */
     128,                         /* Input block size in octets */
     { 2,16,840,1,101,3,4,2,7 },  /* ASN.1 OID */
     9,                           /* Length OID */
     &sha3_224_init,
     &sha3_process,
     &sha3_done,
     &sha3_224_test,
     NULL
  };
  
  const struct ltc_hash_descriptor sha3_256_desc =
  {
     "sha3-256",                  /* name of hash */
     18,                          /* internal ID */
     32,                          /* Size of digest in octets */
     128,                         /* Input block size in octets */
     { 2,16,840,1,101,3,4,2,8 },  /* ASN.1 OID */
     9,                           /* Length OID */
     &sha3_256_init,
     &sha3_process,
     &sha3_done,
     &sha3_256_test,
     NULL
  };
  
  const struct ltc_hash_descriptor sha3_384_desc =
  {
     "sha3-384",                  /* name of hash */
     19,                          /* internal ID */
     48,                          /* Size of digest in octets */
     128,                         /* Input block size in octets */
     { 2,16,840,1,101,3,4,2,9 },  /* ASN.1 OID */
     9,                           /* Length OID */
     &sha3_384_init,
     &sha3_process,
     &sha3_done,
     &sha3_384_test,
     NULL
  };
  
  const struct ltc_hash_descriptor sha3_512_desc =
  {
     "sha3-512",                  /* name of hash */
     20,                          /* internal ID */
     64,                          /* Size of digest in octets */
     128,                         /* Input block size in octets */
     { 2,16,840,1,101,3,4,2,10 }, /* ASN.1 OID */
     9,                           /* Length OID */
     &sha3_512_init,
     &sha3_process,
     &sha3_done,
     &sha3_512_test,
     NULL
  };
  
  #define SHA3_KECCAK_SPONGE_WORDS 25 /* 1600 bits > 200 bytes > 25 x ulong64 */
  #define SHA3_KECCAK_ROUNDS 24
  
  static const ulong64 keccakf_rndc[24] = {
     CONST64(0x0000000000000001), CONST64(0x0000000000008082),
     CONST64(0x800000000000808a), CONST64(0x8000000080008000),
     CONST64(0x000000000000808b), CONST64(0x0000000080000001),
     CONST64(0x8000000080008081), CONST64(0x8000000000008009),
     CONST64(0x000000000000008a), CONST64(0x0000000000000088),
     CONST64(0x0000000080008009), CONST64(0x000000008000000a),
     CONST64(0x000000008000808b), CONST64(0x800000000000008b),
     CONST64(0x8000000000008089), CONST64(0x8000000000008003),
     CONST64(0x8000000000008002), CONST64(0x8000000000000080),
     CONST64(0x000000000000800a), CONST64(0x800000008000000a),
     CONST64(0x8000000080008081), CONST64(0x8000000000008080),
     CONST64(0x0000000080000001), CONST64(0x8000000080008008)
  };
  
  static const unsigned keccakf_rotc[24] = {
     1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 2, 14, 27, 41, 56, 8, 25, 43, 62, 18, 39, 61, 20, 44
  };
  
  static const unsigned keccakf_piln[24] = {
     10, 7, 11, 17, 18, 3, 5, 16, 8, 21, 24, 4, 15, 23, 19, 13, 12, 2, 20, 14, 22, 9, 6, 1
  };
  
  static void keccakf(ulong64 s[25])
  {
     int i, j, round;
     ulong64 t, bc[5];
  
     for(round = 0; round < SHA3_KECCAK_ROUNDS; round++) {
        /* Theta */
        for(i = 0; i < 5; i++)
           bc[i] = s[i] ^ s[i + 5] ^ s[i + 10] ^ s[i + 15] ^ s[i + 20];
  
        for(i = 0; i < 5; i++) {
           t = bc[(i + 4) % 5] ^ ROL64(bc[(i + 1) % 5], 1);
           for(j = 0; j < 25; j += 5)
              s[j + i] ^= t;
        }
        /* Rho Pi */
        t = s[1];
        for(i = 0; i < 24; i++) {
           j = keccakf_piln[i];
           bc[0] = s[j];
           s[j] = ROL64(t, keccakf_rotc[i]);
           t = bc[0];
        }
        /* Chi */
        for(j = 0; j < 25; j += 5) {
           for(i = 0; i < 5; i++)
              bc[i] = s[j + i];
           for(i = 0; i < 5; i++)
              s[j + i] ^= (~bc[(i + 1) % 5]) & bc[(i + 2) % 5];
        }
        /* Iota */
        s[0] ^= keccakf_rndc[round];
     }
  }
  
  /* Public Inteface */
  
  int sha3_224_init(hash_state *md)
  {
     LTC_ARGCHK(md != NULL);
     XMEMSET(&md->sha3, 0, sizeof(md->sha3));
     md->sha3.capacity_words = 2 * 224 / (8 * sizeof(ulong64));
     return CRYPT_OK;
  }
  
  int sha3_256_init(hash_state *md)
  {
     LTC_ARGCHK(md != NULL);
     XMEMSET(&md->sha3, 0, sizeof(md->sha3));
     md->sha3.capacity_words = 2 * 256 / (8 * sizeof(ulong64));
     return CRYPT_OK;
  }
  
  int sha3_384_init(hash_state *md)
  {
     LTC_ARGCHK(md != NULL);
     XMEMSET(&md->sha3, 0, sizeof(md->sha3));
     md->sha3.capacity_words = 2 * 384 / (8 * sizeof(ulong64));
     return CRYPT_OK;
  }
  
  int sha3_512_init(hash_state *md)
  {
     LTC_ARGCHK(md != NULL);
     XMEMSET(&md->sha3, 0, sizeof(md->sha3));
     md->sha3.capacity_words = 2 * 512 / (8 * sizeof(ulong64));
     return CRYPT_OK;
  }
  
  int sha3_shake_init(hash_state *md, int num)
  {
     LTC_ARGCHK(md != NULL);
     if (num != 128 && num != 256) return CRYPT_INVALID_ARG;
     XMEMSET(&md->sha3, 0, sizeof(md->sha3));
     md->sha3.capacity_words = (unsigned short)(2 * num / (8 * sizeof(ulong64)));
     return CRYPT_OK;
  }
  
  int sha3_process(hash_state *md, const unsigned char *in, unsigned long inlen)
  {
     /* 0...7 -- how much is needed to have a word */
     unsigned old_tail = (8 - md->sha3.byte_index) & 7;
  
     unsigned long words;
     unsigned tail;
     unsigned long i;
  
     if (inlen == 0) return CRYPT_OK; /* nothing to do */
     LTC_ARGCHK(md != NULL);
     LTC_ARGCHK(in != NULL);
  
     if(inlen < old_tail) {       /* have no complete word or haven't started the word yet */
        while (inlen--) md->sha3.saved |= (ulong64) (*(in++)) << ((md->sha3.byte_index++) * 8);
        return CRYPT_OK;
     }
  
     if(old_tail) {               /* will have one word to process */
        inlen -= old_tail;
        while (old_tail--) md->sha3.saved |= (ulong64) (*(in++)) << ((md->sha3.byte_index++) * 8);
        /* now ready to add saved to the sponge */
        md->sha3.s[md->sha3.word_index] ^= md->sha3.saved;
        md->sha3.byte_index = 0;
        md->sha3.saved = 0;
        if(++md->sha3.word_index == (SHA3_KECCAK_SPONGE_WORDS - md->sha3.capacity_words)) {
           keccakf(md->sha3.s);
           md->sha3.word_index = 0;
        }
     }
  
     /* now work in full words directly from input */
     words = inlen / sizeof(ulong64);
     tail = inlen - words * sizeof(ulong64);
  
     for(i = 0; i < words; i++, in += sizeof(ulong64)) {
        ulong64 t;
        LOAD64L(t, in);
        md->sha3.s[md->sha3.word_index] ^= t;
        if(++md->sha3.word_index == (SHA3_KECCAK_SPONGE_WORDS - md->sha3.capacity_words)) {
           keccakf(md->sha3.s);
           md->sha3.word_index = 0;
        }
     }
  
     /* finally, save the partial word */
     while (tail--) {
        md->sha3.saved |= (ulong64) (*(in++)) << ((md->sha3.byte_index++) * 8);
     }
     return CRYPT_OK;
  }
  
  int sha3_done(hash_state *md, unsigned char *hash)
  {
     unsigned i;
  
     LTC_ARGCHK(md   != NULL);
     LTC_ARGCHK(hash != NULL);
  
     md->sha3.s[md->sha3.word_index] ^= (md->sha3.saved ^ (CONST64(0x06) << (md->sha3.byte_index * 8)));
     md->sha3.s[SHA3_KECCAK_SPONGE_WORDS - md->sha3.capacity_words - 1] ^= CONST64(0x8000000000000000);
     keccakf(md->sha3.s);
  
     /* store sha3.s[] as little-endian bytes into sha3.sb */
     for(i = 0; i < SHA3_KECCAK_SPONGE_WORDS; i++) {
        STORE64L(md->sha3.s[i], md->sha3.sb + i * 8);
     }
  
     XMEMCPY(hash, md->sha3.sb, md->sha3.capacity_words * 4);
     return CRYPT_OK;
  }
  
  int sha3_shake_done(hash_state *md, unsigned char *out, unsigned long outlen)
  {
     /* IMPORTANT NOTE: sha3_shake_done can be called many times */
     unsigned long idx;
     unsigned i;
  
     if (outlen == 0) return CRYPT_OK; /* nothing to do */
     LTC_ARGCHK(md  != NULL);
     LTC_ARGCHK(out != NULL);
  
     if (!md->sha3.xof_flag) {
        /* shake_xof operation must be done only once */
        md->sha3.s[md->sha3.word_index] ^= (md->sha3.saved ^ (CONST64(0x1F) << (md->sha3.byte_index * 8)));
        md->sha3.s[SHA3_KECCAK_SPONGE_WORDS - md->sha3.capacity_words - 1] ^= CONST64(0x8000000000000000);
        keccakf(md->sha3.s);
        /* store sha3.s[] as little-endian bytes into sha3.sb */
        for(i = 0; i < SHA3_KECCAK_SPONGE_WORDS; i++) {
           STORE64L(md->sha3.s[i], md->sha3.sb + i * 8);
        }
        md->sha3.byte_index = 0;
        md->sha3.xof_flag = 1;
     }
  
     for (idx = 0; idx < outlen; idx++) {
        if(md->sha3.byte_index >= (SHA3_KECCAK_SPONGE_WORDS - md->sha3.capacity_words) * 8) {
           keccakf(md->sha3.s);
           /* store sha3.s[] as little-endian bytes into sha3.sb */
           for(i = 0; i < SHA3_KECCAK_SPONGE_WORDS; i++) {
              STORE64L(md->sha3.s[i], md->sha3.sb + i * 8);
           }
           md->sha3.byte_index = 0;
        }
        out[idx] = md->sha3.sb[md->sha3.byte_index++];
     }
     return CRYPT_OK;
  }
  
  int sha3_shake_memory(int num, const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen)
  {
     hash_state md;
     int err;
     LTC_ARGCHK(in  != NULL);
     LTC_ARGCHK(out != NULL);
     LTC_ARGCHK(outlen != NULL);
     if ((err = sha3_shake_init(&md, num))          != CRYPT_OK) return err;
     if ((err = sha3_shake_process(&md, in, inlen)) != CRYPT_OK) return err;
     if ((err = sha3_shake_done(&md, out, *outlen)) != CRYPT_OK) return err;
     return CRYPT_OK;
  }
  
  #endif
  