--- /dev/null
+/* arcfour.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/>.
+*/
+/*
+ * File: arcfour.c
+ * Author: Daniel Otte
+ * email: daniel.otte@rub.de
+ * Date: 2006-06-07
+ * License: GPLv3 or later
+ * Description: Implementation of the ARCFOUR (RC4 compatible) stream cipher algorithm.
+ *
+ */
+
+#include <stdint.h>
+#include "arcfour.h"
+
+/*
+ * length is length of key in bits!
+ */
+
+void arcfour_init(const void *key, uint16_t length_b, arcfour_ctx_t *ctx){
+ uint8_t t;
+ uint8_t x=0,y=0;
+ length_b /= 8;
+ const uint8_t *kptr, *limit;
+ limit = (uint8_t*)key + length_b;
+ kptr = key;
+ do{
+ ctx->s[x]=x;
+ }while(++x);
+
+ do{
+ y += ctx->s[x] + *kptr++;
+ if(kptr==limit){
+ kptr=key;
+ }
+ /* ctx->s[y] <--> ctx->s[x] */
+ t = ctx->s[y];
+ ctx->s[y] = ctx->s[x];
+ ctx->s[x] = t;
+ }while(++x);
+ ctx->i = ctx->j = 0;
+}
+
+uint8_t arcfour_gen(arcfour_ctx_t *ctx){
+ uint8_t t;
+ ctx->i++;
+ ctx->j += ctx->s[ctx->i];
+ /* ctx->s[i] <--> ctx->s[j] */
+ t = ctx->s[ctx->j];
+ ctx->s[ctx->j] = ctx->s[ctx->i];
+ ctx->s[ctx->i] = t;
+ return ctx->s[(ctx->s[ctx->j] + ctx->s[ctx->i]) & 0xff];
+}
+