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Diffstat (limited to 'libavutil/tea.c')
-rw-r--r-- | libavutil/tea.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/libavutil/tea.c b/libavutil/tea.c new file mode 100644 index 0000000000..b138f8bea1 --- /dev/null +++ b/libavutil/tea.c @@ -0,0 +1,121 @@ +/* + * 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; + } + } +} |