## ffmpeg / libavutil / rc4.c @ a02dd7eb

History | View | Annotate | Download (1.57 KB)

1 | 80b1c5a8 | Reimar DÃ¶ffinger | ```
/*
``` |
---|---|---|---|

2 | ```
* RC4 encryption/decryption/pseudo-random number generator
``` |
||

3 | ```
* Copyright (c) 2007 Reimar Doeffinger
``` |
||

4 | ```
*
``` |
||

5 | d5a8a023 | Diego Biurrun | ```
* loosely based on LibTomCrypt by Tom St Denis
``` |

6 | ```
*
``` |
||

7 | 80b1c5a8 | Reimar DÃ¶ffinger | ```
* This file is part of FFmpeg.
``` |

8 | ```
*
``` |
||

9 | ```
* FFmpeg is free software; you can redistribute it and/or
``` |
||

10 | ```
* modify it under the terms of the GNU Lesser General Public
``` |
||

11 | ```
* License as published by the Free Software Foundation; either
``` |
||

12 | ```
* version 2.1 of the License, or (at your option) any later version.
``` |
||

13 | ```
*
``` |
||

14 | ```
* FFmpeg is distributed in the hope that it will be useful,
``` |
||

15 | ```
* but WITHOUT ANY WARRANTY; without even the implied warranty of
``` |
||

16 | ```
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
``` |
||

17 | ```
* Lesser General Public License for more details.
``` |
||

18 | ```
*
``` |
||

19 | ```
* You should have received a copy of the GNU Lesser General Public
``` |
||

20 | ```
* License along with FFmpeg; if not, write to the Free Software
``` |
||

21 | ```
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
``` |
||

22 | ```
*/
``` |
||

23 | #include "common.h" |
||

24 | #include "rc4.h" |
||

25 | |||

26 | void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) { |
||

27 | ```
int i, j;
``` |
||

28 | uint8_t x, y; |
||

29 | ```
uint8_t state[256];
``` |
||

30 | for (i = 0; i < 256; i++) |
||

31 | state[i] = i; |
||

32 | ```
y = 0;
``` |
||

33 | ```
// j is i % keylen
``` |
||

34 | for (j = 0, i = 0; i < 256; i++, j++) { |
||

35 | if (j == keylen) j = 0; |
||

36 | y += state[i] + key[j]; |
||

37 | FFSWAP(uint8_t, state[i], state[y]); |
||

38 | } |
||

39 | ```
// state initialized, now do the real encryption
``` |
||

40 | x = 1; y = state[1]; |
||

41 | while (datalen-- > 0) { |
||

42 | uint8_t sum = state[x] + state[y]; |
||

43 | FFSWAP(uint8_t, state[x], state[y]); |
||

44 | *data++ ^= state[sum]; |
||

45 | x++; |
||

46 | y += state[x]; |
||

47 | } |
||

48 | } |