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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* |
| 2 | * RC4 encryption/decryption/pseudo-random number generator |
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| 3 | * Copyright (c) 2007 Reimar Doeffinger |
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| 4 | * |
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| 5 | * loosely based on LibTomCrypt by Tom St Denis |
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| 6 | * |
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| 7 | * This file is part of FFmpeg. |
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| 8 | * |
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| 9 | * FFmpeg is free software; you can redistribute it and/or |
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| 10 | * modify it under the terms of the GNU Lesser General Public |
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| 11 | * License as published by the Free Software Foundation; either |
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| 12 | * version 2.1 of the License, or (at your option) any later version. |
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| 13 | * |
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| 14 | * FFmpeg is distributed in the hope that it will be useful, |
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| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 17 | * Lesser General Public License for more details. |
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| 18 | * |
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| 19 | * You should have received a copy of the GNU Lesser General Public |
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| 20 | * License along with FFmpeg; if not, write to the Free Software |
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| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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| 22 | */ |
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| 23 | #include "avutil.h" |
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| 24 | #include "common.h" |
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| 25 | #include "rc4.h" |
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| 26 | |||
| 27 | typedef struct AVRC4 AVRC4; |
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| 28 | |||
| 29 | int av_rc4_init(AVRC4 *r, const uint8_t *key, int key_bits, int decrypt) { |
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| 30 | int i, j; |
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| 31 | uint8_t y; |
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| 32 | uint8_t *state = r->state; |
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| 33 | int keylen = key_bits >> 3; |
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| 34 | if (key_bits & 7) |
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| 35 | return -1; |
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| 36 | for (i = 0; i < 256; i++) |
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| 37 | state[i] = i; |
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| 38 | y = 0; |
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| 39 | // j is i % keylen |
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| 40 | for (j = 0, i = 0; i < 256; i++, j++) { |
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| 41 | if (j == keylen) j = 0; |
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| 42 | y += state[i] + key[j]; |
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| 43 | FFSWAP(uint8_t, state[i], state[y]); |
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| 44 | } |
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| 45 | r->x = 1; |
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| 46 | r->y = state[1]; |
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| 47 | return 0; |
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| 48 | } |
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| 49 | |||
| 50 | void av_rc4_crypt(AVRC4 *r, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) { |
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| 51 | uint8_t x = r->x, y = r->y; |
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| 52 | uint8_t *state = r->state; |
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| 53 | while (count-- > 0) { |
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| 54 | uint8_t sum = state[x] + state[y]; |
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| 55 | FFSWAP(uint8_t, state[x], state[y]); |
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| 56 | *dst++ = src ? *src++ ^ state[sum] : state[sum]; |
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| 57 | x++; |
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| 58 | y += state[x]; |
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| 59 | } |
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| 60 | r->x = x; r->y = y; |
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| 61 | } |