From 80b1c5a8580c84e45ee1304a6be21a629aca252f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Reimar=20D=C3=B6ffinger?= Date: Sat, 13 Oct 2007 10:42:11 +0000 Subject: [PATCH] Add RC4 encryption/decryption function Originally committed as revision 10723 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavutil/Makefile | 1 + libavutil/rc4.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++ libavutil/rc4.h | 1 + 3 files changed, 50 insertions(+) create mode 100644 libavutil/rc4.c create mode 100644 libavutil/rc4.h diff --git a/libavutil/Makefile b/libavutil/Makefile index cea3cab55b..bb10fd6774 100644 --- a/libavutil/Makefile +++ b/libavutil/Makefile @@ -14,6 +14,7 @@ OBJS = adler32.o \ mem.o \ random.o \ rational.o \ + rc4.o \ string.o \ tree.o \ diff --git a/libavutil/rc4.c b/libavutil/rc4.c new file mode 100644 index 0000000000..e59dac853e --- /dev/null +++ b/libavutil/rc4.c @@ -0,0 +1,48 @@ +/* + * RC4 encryption/decryption/pseudo-random number generator + * Copyright (c) 2007 Reimar Doeffinger + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * loosely based on LibTomCrypt by Tom St Denis + */ +#include "common.h" +#include "rc4.h" + +void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) { + int i, j; + uint8_t x, y; + uint8_t state[256]; + for (i = 0; i < 256; i++) + state[i] = i; + y = 0; + // j is i % keylen + for (j = 0, i = 0; i < 256; i++, j++) { + if (j == keylen) j = 0; + y += state[i] + key[j]; + FFSWAP(uint8_t, state[i], state[y]); + } + // state initialized, now do the real encryption + x = 1; y = state[1]; + while (datalen-- > 0) { + uint8_t sum = state[x] + state[y]; + FFSWAP(uint8_t, state[x], state[y]); + *data++ ^= state[sum]; + x++; + y += state[x]; + } +} diff --git a/libavutil/rc4.h b/libavutil/rc4.h new file mode 100644 index 0000000000..f4d5c08892 --- /dev/null +++ b/libavutil/rc4.h @@ -0,0 +1 @@ +void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen);