Botan: src/block/xtea/xtea.cpp Source File

Botan 1.10.16

xtea.cpp
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1 /*
2 * XTEA
3 * (C) 1999-2009 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7
8 #include <botan/xtea.h>
9 #include <botan/loadstor.h>
10
11 namespace Botan {
12
13 namespace {
14
15 void xtea_encrypt_4(const byte in[32], byte out[32], const u32bit EK[64])
16 {
17 u32bit L0, R0, L1, R1, L2, R2, L3, R3;
18 load_be(in, L0, R0, L1, R1, L2, R2, L3, R3);
19
20 for(size_t i = 0; i != 32; ++i)
21 {
22 L0 += (((R0 << 4) ^ (R0 >> 5)) + R0) ^ EK[2*i];
23 L1 += (((R1 << 4) ^ (R1 >> 5)) + R1) ^ EK[2*i];
24 L2 += (((R2 << 4) ^ (R2 >> 5)) + R2) ^ EK[2*i];
25 L3 += (((R3 << 4) ^ (R3 >> 5)) + R3) ^ EK[2*i];
26
27 R0 += (((L0 << 4) ^ (L0 >> 5)) + L0) ^ EK[2*i+1];
28 R1 += (((L1 << 4) ^ (L1 >> 5)) + L1) ^ EK[2*i+1];
29 R2 += (((L2 << 4) ^ (L2 >> 5)) + L2) ^ EK[2*i+1];
30 R3 += (((L3 << 4) ^ (L3 >> 5)) + L3) ^ EK[2*i+1];
31 }
32
33 store_be(out, L0, R0, L1, R1, L2, R2, L3, R3);
34 }
35
36 void xtea_decrypt_4(const byte in[32], byte out[32], const u32bit EK[64])
37 {
38 u32bit L0, R0, L1, R1, L2, R2, L3, R3;
39 load_be(in, L0, R0, L1, R1, L2, R2, L3, R3);
40
41 for(size_t i = 0; i != 32; ++i)
42 {
43 R0 -= (((L0 << 4) ^ (L0 >> 5)) + L0) ^ EK[63 - 2*i];
44 R1 -= (((L1 << 4) ^ (L1 >> 5)) + L1) ^ EK[63 - 2*i];
45 R2 -= (((L2 << 4) ^ (L2 >> 5)) + L2) ^ EK[63 - 2*i];
46 R3 -= (((L3 << 4) ^ (L3 >> 5)) + L3) ^ EK[63 - 2*i];
47
48 L0 -= (((R0 << 4) ^ (R0 >> 5)) + R0) ^ EK[62 - 2*i];
49 L1 -= (((R1 << 4) ^ (R1 >> 5)) + R1) ^ EK[62 - 2*i];
50 L2 -= (((R2 << 4) ^ (R2 >> 5)) + R2) ^ EK[62 - 2*i];
51 L3 -= (((R3 << 4) ^ (R3 >> 5)) + R3) ^ EK[62 - 2*i];
52 }
53
54 store_be(out, L0, R0, L1, R1, L2, R2, L3, R3);
55 }
56
57 }
58
59 /*
60 * XTEA Encryption
61 */
62 void XTEA::encrypt_n(const byte in[], byte out[], size_t blocks) const
63 {
64 while(blocks >= 4)
65 {
66 xtea_encrypt_4(in, out, &(this->EK[0]));
67 in += 4 * BLOCK_SIZE;
68 out += 4 * BLOCK_SIZE;
69 blocks -= 4;
70 }
71
72 for(size_t i = 0; i != blocks; ++i)
73 {
74 u32bit L = load_be<u32bit>(in, 0);
75 u32bit R = load_be<u32bit>(in, 1);
76
77 for(size_t j = 0; j != 32; ++j)
78 {
79 L += (((R << 4) ^ (R >> 5)) + R) ^ EK[2*j];
80 R += (((L << 4) ^ (L >> 5)) + L) ^ EK[2*j+1];
81 }
82
83 store_be(out, L, R);
84
85 in += BLOCK_SIZE;
86 out += BLOCK_SIZE;
87 }
88 }
89
90 /*
91 * XTEA Decryption
92 */
93 void XTEA::decrypt_n(const byte in[], byte out[], size_t blocks) const
94 {
95 while(blocks >= 4)
96 {
97 xtea_decrypt_4(in, out, &(this->EK[0]));
98 in += 4 * BLOCK_SIZE;
99 out += 4 * BLOCK_SIZE;
100 blocks -= 4;
101 }
102
103 for(size_t i = 0; i != blocks; ++i)
104 {
105 u32bit L = load_be<u32bit>(in, 0);
106 u32bit R = load_be<u32bit>(in, 1);
107
108 for(size_t j = 0; j != 32; ++j)
109 {
110 R -= (((L << 4) ^ (L >> 5)) + L) ^ EK[63 - 2*j];
111 L -= (((R << 4) ^ (R >> 5)) + R) ^ EK[62 - 2*j];
112 }
113
114 store_be(out, L, R);
115
116 in += BLOCK_SIZE;
117 out += BLOCK_SIZE;
118 }
119 }
120
121 /*
122 * XTEA Key Schedule
123 */
124 void XTEA::key_schedule(const byte key[], size_t)
125 {
126 SecureVector<u32bit> UK(4);
127 for(size_t i = 0; i != 4; ++i)
128 UK[i] = load_be<u32bit>(key, i);
129
130 u32bit D = 0;
131 for(size_t i = 0; i != 64; i += 2)
132 {
133 EK[i ] = D + UK[D % 4];
134 D += 0x9E3779B9;
135 EK[i+1] = D + UK[(D >> 11) % 4];
136 }
137 }
138
139 }
Botan::load_be
T load_be(const byte in[], size_t off)
Definition: loadstor.h:100
Botan::XTEA::encrypt_n
void encrypt_n(const byte in[], byte out[], size_t blocks) const
Definition: xtea.cpp:62
Botan::Block_Cipher_Fixed_Params< 8, 16 >::BLOCK_SIZE
Definition: block_cipher.h:107
R0
#define R0
Definition: asm_x86_64.h:51
Botan::byte
unsigned char byte
Definition: types.h:22
R2
#define R2
Definition: asm_x86_64.h:53
Botan
Definition: algo_base.h:14
R1
#define R1
Definition: asm_x86_64.h:52
Botan::load_be< u32bit >
u32bit load_be< u32bit >(const byte in[], size_t off)
Definition: loadstor.h:166
Botan::store_be
void store_be(u16bit in, byte out[2])
Definition: loadstor.h:412
Botan::SecureVector< u32bit >
R3
#define R3
Definition: asm_x86_64.h:55
Botan::XTEA::decrypt_n
void decrypt_n(const byte in[], byte out[], size_t blocks) const
Definition: xtea.cpp:93
Botan::u32bit
unsigned int u32bit
Definition: types.h:32