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/* sha256.c - an implementation of SHA-256/224 hash functions
 * based on FIPS 180-3 (Federal Information Processing Standart).
 *
 * Copyright (c) 2010, Aleksey Kravchenko <rhash.admin@gmail.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE  INCLUDING ALL IMPLIED WARRANTIES OF  MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT,  OR CONSEQUENTIAL DAMAGES  OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE,  DATA OR PROFITS,  WHETHER IN AN ACTION OF CONTRACT,  NEGLIGENCE
 * OR OTHER TORTIOUS ACTION,  ARISING OUT OF  OR IN CONNECTION  WITH THE USE  OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#include <string.h>
#include "byte_order.h"
#include "sha256.h"

/* SHA-224 and SHA-256 constants for 64 rounds. These words represent
 * the first 32 bits of the fractional parts of the cube
 * roots of the first 64 prime numbers. */
static const unsigned rhash_k256[64] = {
	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
	0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
	0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
	0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
	0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
	0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
	0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
	0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
	0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

/* The SHA256/224 functions defined by FIPS 180-3, 4.1.2 */
/* Optimized version of Ch(x,y,z)=((x & y) | (~x & z)) */
#define Ch(x,y,z)  ((z) ^ ((x) & ((y) ^ (z))))
/* Optimized version of Maj(x,y,z)=((x & y) ^ (x & z) ^ (y & z)) */
#define Maj(x,y,z) (((x) & (y)) ^ ((z) & ((x) ^ (y))))

#define Sigma0(x) (ROTR32((x), 2) ^ ROTR32((x), 13) ^ ROTR32((x), 22))
#define Sigma1(x) (ROTR32((x), 6) ^ ROTR32((x), 11) ^ ROTR32((x), 25))
#define sigma0(x) (ROTR32((x), 7) ^ ROTR32((x), 18) ^ ((x) >>  3))
#define sigma1(x) (ROTR32((x),17) ^ ROTR32((x), 19) ^ ((x) >> 10))

/* Recalculate element n-th of circular buffer W using formula
 *   W[n] = sigma1(W[n - 2]) + W[n - 7] + sigma0(W[n - 15]) + W[n - 16]; */
#define RECALCULATE_W(W,n) (W[n] += \
	(sigma1(W[(n - 2) & 15]) + W[(n - 7) & 15] + sigma0(W[(n - 15) & 15])))

#define ROUND(a,b,c,d,e,f,g,h,k,data) { \
	unsigned T1 = h + Sigma1(e) + Ch(e,f,g) + k + (data); \
	d += T1, h = T1 + Sigma0(a) + Maj(a,b,c); }
#define ROUND_1_16(a,b,c,d,e,f,g,h,n) \
	ROUND(a,b,c,d,e,f,g,h, rhash_k256[n], W[n] = be2me_32(block[n]))
#define ROUND_17_64(a,b,c,d,e,f,g,h,n) \
	ROUND(a,b,c,d,e,f,g,h, k[n], RECALCULATE_W(W, n))

/**
 * Initialize context before calculaing hash.
 *
 * @param ctx context to initialize
 */
void rhash_sha256_init(sha256_ctx* ctx)
{
	/* Initial values. These words were obtained by taking the first 32
	 * bits of the fractional parts of the square roots of the first
	 * eight prime numbers. */
	static const unsigned SHA256_H0[8] = {
		0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
		0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
	};

	ctx->length = 0;
	ctx->digest_length = sha256_hash_size;

	/* initialize algorithm state */
	memcpy(ctx->hash, SHA256_H0, sizeof(ctx->hash));
}

/**
 * Initialize context before calculaing hash.
 *
 * @param ctx context to initialize
 */
void rhash_sha224_init(struct sha256_ctx* ctx)
{
	/* Initial values from FIPS 180-3. These words were obtained by taking
	 * bits from 33th to 64th of the fractional parts of the square
	 * roots of ninth through sixteenth prime numbers. */
	static const unsigned SHA224_H0[8] = {
		0xc1059ed8, 0x367cd507, 0x3070dd17, 0xf70e5939,
		0xffc00b31, 0x68581511, 0x64f98fa7, 0xbefa4fa4
	};

	ctx->length = 0;
	ctx->digest_length = sha224_hash_size;

	memcpy(ctx->hash, SHA224_H0, sizeof(ctx->hash));
}

/**
 * The core transformation. Process a 512-bit block.
 *
 * @param hash algorithm state
 * @param block the message block to process