FFmpeg
tea.c
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1 /*
2  * A 32-bit implementation of the TEA algorithm
3  * Copyright (c) 2015 Vesselin Bontchev
4  *
5  * Loosely based on the implementation of David Wheeler and Roger Needham,
6  * https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm#Reference_code
7  *
8  * This file is part of FFmpeg.
9  *
10  * FFmpeg is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU Lesser General Public
12  * License as published by the Free Software Foundation; either
13  * version 2.1 of the License, or (at your option) any later version.
14  *
15  * FFmpeg is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18  * Lesser General Public License for more details.
19  *
20  * You should have received a copy of the GNU Lesser General Public
21  * License along with FFmpeg; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23  */
24 
25 #include "avutil.h"
26 #include "common.h"
27 #include "intreadwrite.h"
28 #include "tea.h"
29 
30 typedef struct AVTEA {
31  uint32_t key[16];
32  int rounds;
33 } AVTEA;
34 
35 struct AVTEA *av_tea_alloc(void)
36 {
37  return av_mallocz(sizeof(struct AVTEA));
38 }
39 
40 const int av_tea_size = sizeof(AVTEA);
41 
42 void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
43 {
44  int i;
45 
46  for (i = 0; i < 4; i++)
47  ctx->key[i] = AV_RB32(key + (i << 2));
48 
49  ctx->rounds = rounds;
50 }
51 
52 static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
53  int decrypt, uint8_t *iv)
54 {
55  uint32_t v0, v1;
56  int rounds = ctx->rounds;
57  uint32_t k0, k1, k2, k3;
58  k0 = ctx->key[0];
59  k1 = ctx->key[1];
60  k2 = ctx->key[2];
61  k3 = ctx->key[3];
62 
63  v0 = AV_RB32(src);
64  v1 = AV_RB32(src + 4);
65 
66  if (decrypt) {
67  int i;
68  uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2);
69 
70  for (i = 0; i < rounds / 2; i++) {
71  v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
72  v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
73  sum -= delta;
74  }
75  if (iv) {
76  v0 ^= AV_RB32(iv);
77  v1 ^= AV_RB32(iv + 4);
78  memcpy(iv, src, 8);
79  }
80  } else {
81  int i;
82  uint32_t sum = 0, delta = 0x9E3779B9U;
83 
84  for (i = 0; i < rounds / 2; i++) {
85  sum += delta;
86  v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
87  v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
88  }
89  }
90 
91  AV_WB32(dst, v0);
92  AV_WB32(dst + 4, v1);
93 }
94 
95 void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
96  uint8_t *iv, int decrypt)
97 {
98  int i;
99 
100  if (decrypt) {
101  while (count--) {
102  tea_crypt_ecb(ctx, dst, src, decrypt, iv);
103 
104  src += 8;
105  dst += 8;
106  }
107  } else {
108  while (count--) {
109  if (iv) {
110  for (i = 0; i < 8; i++)
111  dst[i] = src[i] ^ iv[i];
112  tea_crypt_ecb(ctx, dst, dst, decrypt, NULL);
113  memcpy(iv, dst, 8);
114  } else {
115  tea_crypt_ecb(ctx, dst, src, decrypt, NULL);
116  }
117  src += 8;
118  dst += 8;
119  }
120  }
121 }
static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int decrypt, uint8_t *iv)
Definition: tea.c:52
#define NULL
Definition: coverity.c:32
Convenience header that includes libavutil&#39;s core.
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:236
GLfloat v0
Definition: opengl_enc.c:106
#define src
Definition: vp8dsp.c:254
struct AVTEA * av_tea_alloc(void)
Allocate an AVTEA context To free the struct: av_free(ptr)
Definition: tea.c:35
uint8_t
float delta
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32
Definition: bytestream.h:87
Definition: tea.c:30
#define U(x)
Definition: vp56_arith.h:37
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
GLsizei count
Definition: opengl_enc.c:108
Public header for libavutil TEA algorithm.
void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt)
Encrypt or decrypt a buffer using a previously initialized context.
Definition: tea.c:95
AVFormatContext * ctx
Definition: movenc.c:48
int rounds
Definition: tea.c:32
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
const int av_tea_size
Definition: tea.c:40
common internal and external API header
void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
Initialize an AVTEA context.
Definition: tea.c:42
uint32_t key[16]
Definition: tea.c:31