| /* |
| * 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; |
| } |
| } |
| } |