gfiber / vendor / opensource / ffmpeg / 3d15d128df6c42df883fe3aedbbd2ef50085217f / . / libavutil / rc4.c

/* | |

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

* Copyright (c) 2007 Reimar Doeffinger | |

* | |

* loosely based on LibTomCrypt by Tom St Denis | |

* | |

* 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 | |

*/ | |

#include "avutil.h" | |

#include "common.h" | |

#include "rc4.h" | |

typedef struct AVRC4 AVRC4; | |

int av_rc4_init(AVRC4 *r, const uint8_t *key, int key_bits, int decrypt) { | |

int i, j; | |

uint8_t y; | |

uint8_t *state = r->state; | |

int keylen = key_bits >> 3; | |

if (key_bits & 7) | |

return -1; | |

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]); | |

} | |

r->x = 1; | |

r->y = state[1]; | |

return 0; | |

} | |

void av_rc4_crypt(AVRC4 *r, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) { | |

uint8_t x = r->x, y = r->y; | |

uint8_t *state = r->state; | |

while (count-- > 0) { | |

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

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

*dst++ = src ? *src++ ^ state[sum] : state[sum]; | |

x++; | |

y += state[x]; | |

} | |

r->x = x; r->y = y; | |

} |