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48 lines
1.6 KiB
48 lines
1.6 KiB
/* |
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* RC4 encryption/decryption/pseudo-random number generator |
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* Copyright (c) 2007 Reimar Doeffinger |
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* |
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* loosely based on LibTomCrypt by Tom St Denis |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "common.h" |
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#include "rc4.h" |
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void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) { |
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int i, j; |
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uint8_t x, y; |
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uint8_t state[256]; |
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for (i = 0; i < 256; i++) |
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state[i] = i; |
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y = 0; |
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// j is i % keylen |
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for (j = 0, i = 0; i < 256; i++, j++) { |
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if (j == keylen) j = 0; |
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y += state[i] + key[j]; |
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FFSWAP(uint8_t, state[i], state[y]); |
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} |
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// state initialized, now do the real encryption |
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x = 1; y = state[1]; |
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while (datalen-- > 0) { |
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uint8_t sum = state[x] + state[y]; |
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FFSWAP(uint8_t, state[x], state[y]); |
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*data++ ^= state[sum]; |
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x++; |
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y += state[x]; |
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} |
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}
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