181 lines
7.9 KiB
C
181 lines
7.9 KiB
C
/*
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* AES 128 bit decryption
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* Copyright (c) 2007 Reimar Doeffinger.
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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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* Based on public domain AES reference code by Paulo Barreto, Vincent Rijmen
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*/
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#include "common.h"
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#include "aes128.h"
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#ifdef CONFIG_GCRYPT
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AES128Context *aes128_init(void) {
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AES128Context *res = av_malloc(sizeof(*res));
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gcry_cipher_open(&res->ch, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CBC, 0);
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return res;
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}
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void aes128_set_key(AES128Context *c, const uint8_t *key) {
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gcry_cipher_ctl(c->ch, GCRYCTL_SET_KEY, key, 16);
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}
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void aes128_cbc_decrypt(AES128Context *c, uint8_t *mem, int blockcnt, uint8_t *IV) {
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blockcnt <<= 4;
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gcry_cipher_ctl(c->ch, GCRYCTL_SET_IV, IV, 16);
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memcpy(IV, &mem[blockcnt - 16], 16);
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gcry_cipher_decrypt(c->ch, mem, blockcnt, mem, blockcnt);
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}
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#else
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static const uint8_t rcon[10] = {
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0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
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};
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static const uint8_t logtbl[256] = {
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0, 0, 25, 1, 50, 2, 26, 198, 75, 199, 27, 104, 51, 238, 223, 3,
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100, 4, 224, 14, 52, 141, 129, 239, 76, 113, 8, 200, 248, 105, 28, 193,
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125, 194, 29, 181, 249, 185, 39, 106, 77, 228, 166, 114, 154, 201, 9, 120,
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101, 47, 138, 5, 33, 15, 225, 36, 18, 240, 130, 69, 53, 147, 218, 142,
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150, 143, 219, 189, 54, 208, 206, 148, 19, 92, 210, 241, 64, 70, 131, 56,
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102, 221, 253, 48, 191, 6, 139, 98, 179, 37, 226, 152, 34, 136, 145, 16,
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126, 110, 72, 195, 163, 182, 30, 66, 58, 107, 40, 84, 250, 133, 61, 186,
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43, 121, 10, 21, 155, 159, 94, 202, 78, 212, 172, 229, 243, 115, 167, 87,
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175, 88, 168, 80, 244, 234, 214, 116, 79, 174, 233, 213, 231, 230, 173, 232,
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44, 215, 117, 122, 235, 22, 11, 245, 89, 203, 95, 176, 156, 169, 81, 160,
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127, 12, 246, 111, 23, 196, 73, 236, 216, 67, 31, 45, 164, 118, 123, 183,
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204, 187, 62, 90, 251, 96, 177, 134, 59, 82, 161, 108, 170, 85, 41, 157,
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151, 178, 135, 144, 97, 190, 220, 252, 188, 149, 207, 205, 55, 63, 91, 209,
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83, 57, 132, 60, 65, 162, 109, 71, 20, 42, 158, 93, 86, 242, 211, 171,
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68, 17, 146, 217, 35, 32, 46, 137, 180, 124, 184, 38, 119, 153, 227, 165,
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103, 74, 237, 222, 197, 49, 254, 24, 13, 99, 140, 128, 192, 247, 112, 7
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};
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static const uint8_t invsubst[256] = {
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82, 9, 106, 213, 48, 54, 165, 56, 191, 64, 163, 158, 129, 243, 215, 251,
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124, 227, 57, 130, 155, 47, 255, 135, 52, 142, 67, 68, 196, 222, 233, 203,
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84, 123, 148, 50, 166, 194, 35, 61, 238, 76, 149, 11, 66, 250, 195, 78,
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8, 46, 161, 102, 40, 217, 36, 178, 118, 91, 162, 73, 109, 139, 209, 37,
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114, 248, 246, 100, 134, 104, 152, 22, 212, 164, 92, 204, 93, 101, 182, 146,
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108, 112, 72, 80, 253, 237, 185, 218, 94, 21, 70, 87, 167, 141, 157, 132,
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144, 216, 171, 0, 140, 188, 211, 10, 247, 228, 88, 5, 184, 179, 69, 6,
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208, 44, 30, 143, 202, 63, 15, 2, 193, 175, 189, 3, 1, 19, 138, 107,
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58, 145, 17, 65, 79, 103, 220, 234, 151, 242, 207, 206, 240, 180, 230, 115,
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150, 172, 116, 34, 231, 173, 53, 133, 226, 249, 55, 232, 28, 117, 223, 110,
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71, 241, 26, 113, 29, 41, 197, 137, 111, 183, 98, 14, 170, 24, 190, 27,
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252, 86, 62, 75, 198, 210, 121, 32, 154, 219, 192, 254, 120, 205, 90, 244,
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31, 221, 168, 51, 136, 7, 199, 49, 177, 18, 16, 89, 39, 128, 236, 95,
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96, 81, 127, 169, 25, 181, 74, 13, 45, 229, 122, 159, 147, 201, 156, 239,
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160, 224, 59, 77, 174, 42, 245, 176, 200, 235, 187, 60, 131, 83, 153, 97,
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23, 43, 4, 126, 186, 119, 214, 38, 225, 105, 20, 99, 85, 33, 12, 125
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};
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#define XORBLOCK(a, rk) \
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((uint64_t *)(a))[0] ^= ((uint64_t *)(rk))[0];\
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((uint64_t *)(a))[1] ^= ((uint64_t *)(rk))[1];
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#define COPYBLOCK(b, a) \
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((uint64_t *)(b))[0] = ((uint64_t *)(a))[0];\
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((uint64_t *)(b))[1] = ((uint64_t *)(a))[1];
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#define SUBSTSHIFTROWS(b, a) \
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b[0] = invsubst[a[0]]; b[1] = invsubst[a[13]]; b[2] = invsubst[a[10]];\
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b[3] = invsubst[a[7]]; b[4] = invsubst[a[4]]; b[5] = invsubst[a[1]];\
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b[6] = invsubst[a[14]]; b[7] = invsubst[a[11]]; b[8] = invsubst[a[8]];\
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b[9] = invsubst[a[5]]; b[10] = invsubst[a[2]]; b[11] = invsubst[a[15]];\
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b[12] = invsubst[a[12]]; b[13] = invsubst[a[9]]; b[14] = invsubst[a[6]];\
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b[15] = invsubst[a[3]];
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#define INVMIX(b, a) \
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((uint32_t *)(b))[0] = c->multbl[0][a[0]] ^ c->multbl[1][a[1]] ^ c->multbl[2][a[2]] ^ c->multbl[3][a[3]];\
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((uint32_t *)(b))[1] = c->multbl[0][a[4]] ^ c->multbl[1][a[5]] ^ c->multbl[2][a[6]] ^ c->multbl[3][a[7]];\
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((uint32_t *)(b))[2] = c->multbl[0][a[8]] ^ c->multbl[1][a[9]] ^ c->multbl[2][a[10]] ^ c->multbl[3][a[11]];\
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((uint32_t *)(b))[3] = c->multbl[0][a[12]] ^ c->multbl[1][a[13]] ^ c->multbl[2][a[14]] ^ c->multbl[3][a[15]];
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#define MUL(a, b) ((a && b) ? invlogtbl[(logtbl[a] + logtbl[b])%255] : 0)
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AES128Context *aes128_init(void) {
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AES128Context *c = av_mallocz(sizeof(*c));
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uint8_t *invlogtbl = av_malloc(256);
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uint8_t *tbl0, *tbl1, *tbl2, *tbl3;
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int i;
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for (i = 0; i < 256; i++) {
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c->subst[invsubst[i]] = i;
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invlogtbl[logtbl[i]] = i;
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}
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invlogtbl[255] = 1;
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tbl0 = (uint8_t *)c->multbl[0];
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tbl1 = (uint8_t *)c->multbl[1];
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tbl2 = (uint8_t *)c->multbl[2];;
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tbl3 = (uint8_t *)c->multbl[3];
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for (i = 0; i < 256; i++) {
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tbl0[4*i+0] = MUL(0xe, i); tbl0[4*i+1] = MUL(0x9, i);
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tbl0[4*i+2] = MUL(0xd, i); tbl0[4*i+3] = MUL(0xb, i);
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tbl1[4*i+0] = MUL(0xb, i); tbl1[4*i+1] = MUL(0xe, i);
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tbl1[4*i+2] = MUL(0x9, i); tbl1[4*i+3] = MUL(0xd, i);
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tbl2[4*i+0] = MUL(0xd, i); tbl2[4*i+1] = MUL(0xb, i);
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tbl2[4*i+2] = MUL(0xe, i); tbl2[4*i+3] = MUL(0x9, i);
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tbl3[4*i+0] = MUL(0x9, i); tbl3[4*i+1] = MUL(0xd, i);
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tbl3[4*i+2] = MUL(0xb, i); tbl3[4*i+3] = MUL(0xe, i);
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}
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av_free(invlogtbl);
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return c;
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}
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void aes128_set_key(AES128Context *c, const uint8_t *key) {
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uint8_t tmp[4][4];
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long r, i, j;
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memcpy(tmp, key, 16);
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memcpy(c->key[0], tmp, 16);
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for (r = 1; r < 11; r++) {
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for (i = 0; i < 4; i++) tmp[0][i] ^= c->subst[tmp[3][(i+1)&3]];
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tmp[0][0] ^= rcon[r - 1];
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for (i = 0; i < 4; i++) for(j = 1; j < 4; j++) tmp[j][i] ^= tmp[j-1][i];
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memcpy(c->key[r], tmp, 16);
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}
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}
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static void aes128_decrypt_block(AES128Context *c, uint8_t *block) {
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long r = 8;
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uint8_t tmp[16];
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XORBLOCK(block, c->key[10]);
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SUBSTSHIFTROWS(tmp, block);
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XORBLOCK(tmp, c->key[9]);
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INVMIX(tmp, tmp);
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SUBSTSHIFTROWS(block, tmp);
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do {
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XORBLOCK(block, c->key[r]);
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INVMIX(tmp, block);
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SUBSTSHIFTROWS(block, tmp);
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} while (--r);
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XORBLOCK(block, c->key[0]);
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}
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void aes128_cbc_decrypt(AES128Context *c, uint8_t *mem, int blockcnt, uint8_t *IV) {
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uint8_t tmp[16];
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if (blockcnt & 1) {
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COPYBLOCK(tmp, mem);
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aes128_decrypt_block(c, mem);
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XORBLOCK(mem, IV);
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COPYBLOCK(IV, tmp);
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mem += 16;
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}
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blockcnt >>= 1;
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while (blockcnt-- > 0) {
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COPYBLOCK(tmp, mem);
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aes128_decrypt_block(c, mem);
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XORBLOCK(mem, IV);
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mem += 16;
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COPYBLOCK(IV, mem);
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aes128_decrypt_block(c, mem);
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XORBLOCK(mem, tmp);
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mem += 16;
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}
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}
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#endif
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