mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-27 01:42:20 +00:00
62 lines
1.9 KiB
C
62 lines
1.9 KiB
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 Libav.
|
|
*
|
|
* Libav 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.
|
|
*
|
|
* Libav 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 Libav; 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;
|
|
}
|