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3d1690b8c6
It's been argued that the benefits of the current implementation far outweight those of making the structs opaque. This deprecation is not present in any release, so it can be safely removed. Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com> Signed-off-by: James Almer <jamrial@gmail.com>
66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
/*
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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 "avutil.h"
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#include "common.h"
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#include "mem.h"
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#include "rc4.h"
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AVRC4 *av_rc4_alloc(void)
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{
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return av_mallocz(sizeof(struct AVRC4));
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}
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int av_rc4_init(AVRC4 *r, const uint8_t *key, int key_bits, int decrypt) {
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int i, j;
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uint8_t y;
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uint8_t *state = r->state;
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int keylen = key_bits >> 3;
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if (key_bits & 7)
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return -1;
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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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r->x = 1;
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r->y = state[1];
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return 0;
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}
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void av_rc4_crypt(AVRC4 *r, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) {
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uint8_t x = r->x, y = r->y;
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uint8_t *state = r->state;
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while (count-- > 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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*dst++ = src ? *src++ ^ state[sum] : state[sum];
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x++;
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y += state[x];
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}
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r->x = x; r->y = y;
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}
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