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/*
* A 32-bit implementation of the TEA algorithm
* Copyright (c) 2015 Vesselin Bontchev
*
* Loosely based on the implementation of David Wheeler and Roger Needham,
* https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm#Reference_code
*
* 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 <string.h>
#include "intreadwrite.h"
#include "mem.h"
#include "tea.h"
typedef struct AVTEA {
uint32_t key[16];
int rounds;
} AVTEA;
struct AVTEA *av_tea_alloc(void)
{
return av_mallocz(sizeof(struct AVTEA));
}
const int av_tea_size = sizeof(AVTEA);
void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
{
int i;
for (i = 0; i < 4; i++)
ctx->key[i] = AV_RB32(key + (i << 2));
ctx->rounds = rounds;
}
static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
int decrypt, uint8_t *iv)
{
uint32_t v0, v1;
int rounds = ctx->rounds;
uint32_t k0, k1, k2, k3;
k0 = ctx->key[0];
k1 = ctx->key[1];
k2 = ctx->key[2];
k3 = ctx->key[3];
v0 = AV_RB32(src);
v1 = AV_RB32(src + 4);
if (decrypt) {
int i;
uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2);
for (i = 0; i < rounds / 2; i++) {
v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
sum -= delta;
}
if (iv) {
v0 ^= AV_RB32(iv);
v1 ^= AV_RB32(iv + 4);
memcpy(iv, src, 8);
}
} else {
int i;
uint32_t sum = 0, delta = 0x9E3779B9U;
for (i = 0; i < rounds / 2; i++) {
sum += delta;
v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
}
}
AV_WB32(dst, v0);
AV_WB32(dst + 4, v1);
}
void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
uint8_t *iv, int decrypt)
{
int i;
if (decrypt) {
while (count--) {
tea_crypt_ecb(ctx, dst, src, decrypt, iv);
src += 8;
dst += 8;
}
} else {
while (count--) {
if (iv) {
for (i = 0; i < 8; i++)
dst[i] = src[i] ^ iv[i];
tea_crypt_ecb(ctx, dst, dst, decrypt, NULL);
memcpy(iv, dst, 8);
} else {
tea_crypt_ecb(ctx, dst, src, decrypt, NULL);
}
src += 8;
dst += 8;
}
}
}
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