--- /dev/null
+/* threefish512_dec.c */
+/*
+ This file is part of the AVR-Crypto-Lib.
+ Copyright (C) 2009 Daniel Otte (daniel.otte@rub.de)
+
+ 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 daniel.otte@rub.de
+ * \date 2009-03-22
+ * \license GPLv3 or later
+ *
+ *
+ *
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include "threefish.h"
+
+
+#define X(a) (((uint64_t*)data)[(a)])
+
+
+static
+void permute_inv8(void* data){
+ uint64_t t;
+ t = X(6);
+ X(6) = X(4);
+ X(4) = X(2);
+ X(2) = X(0);
+ X(0) = t;
+ t = X(7);
+ X(7) = X(3);
+ X(3) = t;
+}
+
+static
+void add_key_8(void* data, const threefish512_ctx_t* ctx, uint8_t s){
+ uint8_t i;
+ for(i=0; i<5; ++i){
+ X(i) -= ctx->k[(s+i)%9];
+ }
+ X(5) -= ctx->k[(s+5)%9] + ctx->t[s%3];
+ X(6) -= ctx->k[(s+6)%9] + ctx->t[(s+1)%3];
+ X(7) -= ctx->k[(s+7)%9] + s;
+}
+
+void threefish512_dec(void* data, const threefish512_ctx_t* ctx){
+ uint8_t i=0,s=18;
+ uint8_t r0[8] = {33, 29, 39, 33, 26, 34, 48, 38};
+ uint8_t r1[8] = {51, 26, 27, 49, 12, 14, 20, 30};
+ uint8_t r2[8] = {39, 11, 41, 8, 58, 15, 43, 50};
+ uint8_t r3[8] = {35, 9, 14, 42, 7, 27, 31, 53};
+ do{
+ if(i%4==0){
+ add_key_8(data, ctx, s);
+ --s;
+ }
+ permute_inv8(data);
+ threefish_invmix((uint8_t*)data + 0, r0[i%8]);
+ threefish_invmix((uint8_t*)data + 16, r1[i%8]);
+ threefish_invmix((uint8_t*)data + 32, r2[i%8]);
+ threefish_invmix((uint8_t*)data + 48, r3[i%8]);
+ ++i;
+ }while(i!=72);
+ add_key_8(data, ctx, s);
+}
+