/* threefish256_enc.c */
/*
    This file is part of the AVR-Crypto-Lib.
    Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
/*
 * \author  Daniel Otte
 * \email   bg@nerilex.org
 * \date    2009-03-12
 * \license GPLv3 or later
 * 
 * 
 * 
 */

#include <stdint.h>
#include <string.h>
#include "threefish.h"

#define X(a) (((uint64_t*)data)[(a)])
static
void permute_4(void *data){
	uint64_t t;
	t = X(1);
	X(1) = X(3);
	X(3) = t;
}

static
void add_key_4(void *data, const threefish256_ctx_t *ctx, uint8_t s){
	X(0) -= ctx->k[(s+0)%5];
	X(1) -= ctx->k[(s+1)%5] + ctx->t[s%3];
	X(2) -= ctx->k[(s+2)%5] + ctx->t[(s+1)%3];
	X(3) -= ctx->k[(s+3)%5] + s;
}

void threefish256_dec(void *data, const threefish256_ctx_t *ctx){
	uint8_t i=0,s=18;
	uint8_t r0[8] = {0x73, 0x13, 0x7b, 0x32, 0x72, 0x2b, 0x44, 0x1b}; 
	uint8_t r1[8] = {0x62, 0x52, 0x43, 0x24, 0x54, 0x6a, 0x34, 0x70};
	do{
		if(i%4==0){
			add_key_4(data, ctx, s);
			--s;
		}
		permute_4(data);
		threefish_invmix(data, r0[i%8]);
		threefish_invmix((uint8_t*)data + 16, r1[i%8]);
		++i;
	}while(i!=72);
	add_key_4(data, ctx, s);
}