text: // keccak.c
  // 19-Nov-11  Markku-Juhani O. Saarinen <mjos@iki.fi>
  // A baseline Keccak (3rd round) implementation.
  
  #include "hash-ops.h"
  #include "keccak.h"
  
  const uint64_t keccakf_rndc[24] =
  {
      0x0000000000000001, 0x0000000000008082, 0x800000000000808a,
      0x8000000080008000, 0x000000000000808b, 0x0000000080000001,
      0x8000000080008081, 0x8000000000008009, 0x000000000000008a,
      0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
      0x000000008000808b, 0x800000000000008b, 0x8000000000008089,
      0x8000000000008003, 0x8000000000008002, 0x8000000000000080,
      0x000000000000800a, 0x800000008000000a, 0x8000000080008081,
      0x8000000000008080, 0x0000000080000001, 0x8000000080008008
  };
  
  const int 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
  };
  
  const int 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
  };
  
  // update the state with given number of rounds
  
  void keccakf(uint64_t st[25], int rounds)
  {
      int i, j, round;
      uint64_t t, bc[5];
  
      for (round = 0; round < rounds; round++) {
  
          // Theta
          for (i = 0; i < 5; i++)
              bc[i] = st[i] ^ st[i + 5] ^ st[i + 10] ^ st[i + 15] ^ st[i + 20];
  
          for (i = 0; i < 5; i++) {
              t = bc[(i + 4) % 5] ^ ROTL64(bc[(i + 1) % 5], 1);
              for (j = 0; j < 25; j += 5)
                  st[j + i] ^= t;
          }
  
          // Rho Pi
          t = st[1];
          for (i = 0; i < 24; i++) {
              j = keccakf_piln[i];
              bc[0] = st[j];
              st[j] = ROTL64(t, keccakf_rotc[i]);
              t = bc[0];
          }
  
          //  Chi
          for (j = 0; j < 25; j += 5) {
              for (i = 0; i < 5; i++)
                  bc[i] = st[j + i];
              for (i = 0; i < 5; i++)
                  st[j + i] ^= (~bc[(i + 1) % 5]) & bc[(i + 2) % 5];
          }
  
          //  Iota
          st[0] ^= keccakf_rndc[round];
      }
  }
  
  // compute a keccak hash (md) of given byte length from "in"
  typedef uint64_t state_t[25];
  
  int keccak(const uint8_t *in, int inlen, uint8_t *md, int mdlen)
  {
      state_t st;
      uint8_t temp[144];
      int i, rsiz, rsizw;
  
      rsiz = sizeof(state_t) == mdlen ? HASH_DATA_AREA : 200 - 2 * mdlen;
      rsizw = rsiz / 8;
  
      memset(st, 0, sizeof(st));
  
      for ( ; inlen >= rsiz; inlen -= rsiz, in += rsiz) {
          for (i = 0; i < rsizw; i++)
              st[i] ^= ((uint64_t *) in)[i];
          keccakf(st, KECCAK_ROUNDS);
      }
  
      // last block and padding
      memcpy(temp, in, inlen);
      temp[inlen++] = 1;
      memset(temp + inlen, 0, rsiz - inlen);
      temp[rsiz - 1] |= 0x80;
  
      for (i = 0; i < rsizw; i++)
          st[i] ^= ((uint64_t *) temp)[i];
  
      keccakf(st, KECCAK_ROUNDS);
  
      memcpy(md, st, mdlen);
  
      return 0;
  }
  
  void keccak1600(const uint8_t *in, int inlen, uint8_t *md)
  {
      keccak(in, inlen, md, sizeof(state_t));
  }
  