updated build system

[arm-crypto-lib.git] / gf256mul / gf256mul.c

diff --git a/gf256mul/gf256mul.c b/gf256mul/gf256mul.c
new file mode 100644 (file)
index 0000000..a473646
--- /dev/null
+++ b/gf256mul/gf256mul.c
@@ -0,0 +1,40 @@
+/* gf256mul.c */
+/*
+    This file is part of the ARM-Crypto-Lib.
+    Copyright (C) 2006-2010  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/>.
+*/
+
+#include <stdint.h>
+
+uint8_t gf256mul(uint8_t a, uint8_t b, uint8_t reducer){
+       uint8_t r=0;
+       while(a&0xFE){
+               if(a&1){
+                       r ^= b;
+               }
+               a >>= 1;
+               if(b&0x80){
+                       b <<= 1;
+                       b ^= reducer;
+               }else{
+                       b <<= 1;
+               }
+       }
+       if(a&1){
+               r ^= b;
+       }
+       return r;
+}