Botan  1.10.9
rc6.cpp
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1 /*
2 * RC6
3 * (C) 1999-2007 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7 
8 #include <botan/rc6.h>
9 #include <botan/loadstor.h>
10 #include <botan/rotate.h>
11 #include <algorithm>
12 
13 namespace Botan {
14 
15 /*
16 * RC6 Encryption
17 */
18 void RC6::encrypt_n(const byte in[], byte out[], size_t blocks) const
19  {
20  for(size_t i = 0; i != blocks; ++i)
21  {
22  u32bit A = load_le<u32bit>(in, 0);
23  u32bit B = load_le<u32bit>(in, 1);
24  u32bit C = load_le<u32bit>(in, 2);
25  u32bit D = load_le<u32bit>(in, 3);
26 
27  B += S[0]; D += S[1];
28 
29  for(size_t j = 0; j != 20; j += 4)
30  {
31  u32bit T1, T2;
32 
33  T1 = rotate_left(B*(2*B+1), 5);
34  T2 = rotate_left(D*(2*D+1), 5);
35  A = rotate_left(A ^ T1, T2 % 32) + S[2*j+2];
36  C = rotate_left(C ^ T2, T1 % 32) + S[2*j+3];
37 
38  T1 = rotate_left(C*(2*C+1), 5);
39  T2 = rotate_left(A*(2*A+1), 5);
40  B = rotate_left(B ^ T1, T2 % 32) + S[2*j+4];
41  D = rotate_left(D ^ T2, T1 % 32) + S[2*j+5];
42 
43  T1 = rotate_left(D*(2*D+1), 5);
44  T2 = rotate_left(B*(2*B+1), 5);
45  C = rotate_left(C ^ T1, T2 % 32) + S[2*j+6];
46  A = rotate_left(A ^ T2, T1 % 32) + S[2*j+7];
47 
48  T1 = rotate_left(A*(2*A+1), 5);
49  T2 = rotate_left(C*(2*C+1), 5);
50  D = rotate_left(D ^ T1, T2 % 32) + S[2*j+8];
51  B = rotate_left(B ^ T2, T1 % 32) + S[2*j+9];
52  }
53 
54  A += S[42]; C += S[43];
55 
56  store_le(out, A, B, C, D);
57 
58  in += BLOCK_SIZE;
59  out += BLOCK_SIZE;
60  }
61  }
62 
63 /*
64 * RC6 Decryption
65 */
66 void RC6::decrypt_n(const byte in[], byte out[], size_t blocks) const
67  {
68  for(size_t i = 0; i != blocks; ++i)
69  {
70  u32bit A = load_le<u32bit>(in, 0);
71  u32bit B = load_le<u32bit>(in, 1);
72  u32bit C = load_le<u32bit>(in, 2);
73  u32bit D = load_le<u32bit>(in, 3);
74 
75  C -= S[43]; A -= S[42];
76 
77  for(size_t j = 0; j != 20; j += 4)
78  {
79  u32bit T1, T2;
80 
81  T1 = rotate_left(A*(2*A+1), 5);
82  T2 = rotate_left(C*(2*C+1), 5);
83  B = rotate_right(B - S[41 - 2*j], T1 % 32) ^ T2;
84  D = rotate_right(D - S[40 - 2*j], T2 % 32) ^ T1;
85 
86  T1 = rotate_left(D*(2*D+1), 5);
87  T2 = rotate_left(B*(2*B+1), 5);
88  A = rotate_right(A - S[39 - 2*j], T1 % 32) ^ T2;
89  C = rotate_right(C - S[38 - 2*j], T2 % 32) ^ T1;
90 
91  T1 = rotate_left(C*(2*C+1), 5);
92  T2 = rotate_left(A*(2*A+1), 5);
93  D = rotate_right(D - S[37 - 2*j], T1 % 32) ^ T2;
94  B = rotate_right(B - S[36 - 2*j], T2 % 32) ^ T1;
95 
96  T1 = rotate_left(B*(2*B+1), 5);
97  T2 = rotate_left(D*(2*D+1), 5);
98  C = rotate_right(C - S[35 - 2*j], T1 % 32) ^ T2;
99  A = rotate_right(A - S[34 - 2*j], T2 % 32) ^ T1;
100  }
101 
102  D -= S[1]; B -= S[0];
103 
104  store_le(out, A, B, C, D);
105 
106  in += BLOCK_SIZE;
107  out += BLOCK_SIZE;
108  }
109  }
110 
111 /*
112 * RC6 Key Schedule
113 */
114 void RC6::key_schedule(const byte key[], size_t length)
115  {
116  const size_t WORD_KEYLENGTH = (((length - 1) / 4) + 1);
117  const size_t MIX_ROUNDS = 3 * std::max(WORD_KEYLENGTH, S.size());
118 
119  S[0] = 0xB7E15163;
120  for(size_t i = 1; i != S.size(); ++i)
121  S[i] = S[i-1] + 0x9E3779B9;
122 
124 
125  for(s32bit i = length-1; i >= 0; --i)
126  K[i/4] = (K[i/4] << 8) + key[i];
127 
128  u32bit A = 0, B = 0;
129  for(size_t i = 0; i != MIX_ROUNDS; ++i)
130  {
131  A = rotate_left(S[i % S.size()] + A + B, 3);
132  B = rotate_left(K[i % WORD_KEYLENGTH] + A + B, (A + B) % 32);
133  S[i % S.size()] = A;
134  K[i % WORD_KEYLENGTH] = B;
135  }
136  }
137 
138 }
void decrypt_n(const byte in[], byte out[], size_t blocks) const
Definition: rc6.cpp:66
void store_le(u16bit in, byte out[2])
Definition: loadstor.h:427
T rotate_left(T input, size_t rot)
Definition: rotate.h:21
signed int s32bit
Definition: types.h:37
unsigned char byte
Definition: types.h:22
T rotate_right(T input, size_t rot)
Definition: rotate.h:34
u32bit load_le< u32bit >(const byte in[], size_t off)
Definition: loadstor.h:183
void encrypt_n(const byte in[], byte out[], size_t blocks) const
Definition: rc6.cpp:18
size_t size() const
Definition: secmem.h:29
unsigned int u32bit
Definition: types.h:32