/* sha256-compress.c
 *
 * The compression function of the sha256 hash function.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001, 2010 Niels Möller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#include "sha.h"

#include "macros.h"

/* A block, treated as a sequence of 32-bit words. */
#define SHA256_DATA_LENGTH 16

#define ROTR(n,x) ((x)>>(n) | ((x)<<(32-(n))))
#define SHR(n,x) ((x)>>(n))

/* The SHA256 functions. The Choice function is the same as the SHA1
   function f1, and the majority function is the same as the SHA1 f3
   function. They can be optimized to save one boolean operation each
   - thanks to Rich Schroeppel, rcs@cs.arizona.edu for discovering
   this */

/* #define Choice(x,y,z) ( ( (x) & (y) ) | ( ~(x) & (z) ) ) */
#define Choice(x,y,z)   ( (z) ^ ( (x) & ( (y) ^ (z) ) ) ) 
/* #define Majority(x,y,z) ( ((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)) ) */
#define Majority(x,y,z) ( ((x) & (y)) ^ ((z) & ((x) ^ (y))) )

#define S0(x) (ROTR(2,(x)) ^ ROTR(13,(x)) ^ ROTR(22,(x))) 
#define S1(x) (ROTR(6,(x)) ^ ROTR(11,(x)) ^ ROTR(25,(x)))

#define s0(x) (ROTR(7,(x)) ^ ROTR(18,(x)) ^ SHR(3,(x)))
#define s1(x) (ROTR(17,(x)) ^ ROTR(19,(x)) ^ SHR(10,(x)))

/* The initial expanding function.  The hash function is defined over an
   64-word expanded input array W, where the first 16 are copies of the input
   data, and the remaining 64 are defined by

        W[ t ] = s1(W[t-2]) + W[t-7] + s0(W[i-15]) + W[i-16]

   This implementation generates these values on the fly in a circular
   buffer - thanks to Colin Plumb, colin@nyx10.cs.du.edu for this
   optimization.
*/

#define EXPAND(W,i) \
( W[(i) & 15 ] += (s1(W[((i)-2) & 15]) + W[((i)-7) & 15] + s0(W[((i)-15) & 15])) )

/* The prototype SHA sub-round.  The fundamental sub-round is:

        T1 = h + S1(e) + Choice(e,f,g) + K[t] + W[t]
	T2 = S0(a) + Majority(a,b,c)
	a' = T1+T2
	b' = a
	c' = b
	d' = c
	e' = d + T1
	f' = e
	g' = f
	h' = g

   but this is implemented by unrolling the loop 8 times and renaming
   the variables
   ( h, a, b, c, d, e, f, g ) = ( a, b, c, d, e, f, g, h ) each
   iteration. */

/* It's crucial that DATA is only used once, as that argument will
 * have side effects. */
#define ROUND(a,b,c,d,e,f,g,h,k,data) do {		\
  uint32_t T = h + S1(e) + Choice(e,f,g) + k + data;	\
  d += T;						\
  h = T + S0(a) + Majority(a,b,c);			\
} while (0)

void
_nettle_sha256_compress(uint32_t *state, const uint8_t *input, const uint32_t *k)
{
  uint32_t data[SHA256_DATA_LENGTH];
  uint32_t A, B, C, D, E, F, G, H;     /* Local vars */
  unsigned i;
  uint32_t *d;

  for (i = 0; i < SHA256_DATA_LENGTH; i++, input+= 4)
    {
      data[i] = READ_UINT32(input);
    }

  /* Set up first buffer and local data buffer */
  A = state[0];
  B = state[1];
  C = state[2];
  D = state[3];
  E = state[4];
  F = state[5];
  G = state[6];
  H = state[7];
  
  /* Heavy mangling */
  /* First 16 subrounds that act on the original data */

  for (i = 0, d = data; i<16; i+=8, k += 8, d+= 8)
    {
      ROUND(A, B, C, D, E, F, G, H, k[0], d[0]);
      ROUND(H, A, B, C, D, E, F, G, k[1], d[1]);
      ROUND(G, H, A, B, C, D, E, F, k[2], d[2]);
      ROUND(F, G, H, A, B, C, D, E, k[3], d[3]);
      ROUND(E, F, G, H, A, B, C, D, k[4], d[4]);
      ROUND(D, E, F, G, H, A, B, C, k[5], d[5]);
      ROUND(C, D, E, F, G, H, A, B, k[6], d[6]);
      ROUND(B, C, D, E, F, G, H, A, k[7], d[7]);
    }
  
  for (; i<64; i += 16, k+= 16)
    {
      ROUND(A, B, C, D, E, F, G, H, k[ 0], EXPAND(data,  0));
      ROUND(H, A, B, C, D, E, F, G, k[ 1], EXPAND(data,  1));
      ROUND(G, H, A, B, C, D, E, F, k[ 2], EXPAND(data,  2));
      ROUND(F, G, H, A, B, C, D, E, k[ 3], EXPAND(data,  3));
      ROUND(E, F, G, H, A, B, C, D, k[ 4], EXPAND(data,  4));
      ROUND(D, E, F, G, H, A, B, C, k[ 5], EXPAND(data,  5));
      ROUND(C, D, E, F, G, H, A, B, k[ 6], EXPAND(data,  6));
      ROUND(B, C, D, E, F, G, H, A, k[ 7], EXPAND(data,  7));
      ROUND(A, B, C, D, E, F, G, H, k[ 8], EXPAND(data,  8));
      ROUND(H, A, B, C, D, E, F, G, k[ 9], EXPAND(data,  9));
      ROUND(G, H, A, B, C, D, E, F, k[10], EXPAND(data, 10));
      ROUND(F, G, H, A, B, C, D, E, k[11], EXPAND(data, 11));
      ROUND(E, F, G, H, A, B, C, D, k[12], EXPAND(data, 12));
      ROUND(D, E, F, G, H, A, B, C, k[13], EXPAND(data, 13));
      ROUND(C, D, E, F, G, H, A, B, k[14], EXPAND(data, 14));
      ROUND(B, C, D, E, F, G, H, A, k[15], EXPAND(data, 15));
    }

  /* Update state */
  state[0] += A;
  state[1] += B;
  state[2] += C;
  state[3] += D;
  state[4] += E;
  state[5] += F;
  state[6] += G;
  state[7] += H;
}
