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Diffstat (limited to 'libavutil/rc4.c')
-rw-r--r-- | libavutil/rc4.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/libavutil/rc4.c b/libavutil/rc4.c new file mode 100644 index 0000000..e59dac8 --- /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]; + } +} |