122 lines
3.2 KiB
C
122 lines
3.2 KiB
C
|
/*
|
||
|
|
* 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 "avutil.h"
|
||
|
|
#include "common.h"
|
||
|
|
#include "intreadwrite.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;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|