1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
/*************************************************
* CFB Mode Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/cfb.h>
#include <botan/lookup.h>
#include <botan/parsing.h>
#include <botan/bit_ops.h>
#include <algorithm>
namespace Botan {
namespace {
/*************************************************
* Check the feedback size *
*************************************************/
void check_feedback(u32bit BLOCK_SIZE, u32bit FEEDBACK_SIZE, u32bit bits,
const std::string& name)
{
if(FEEDBACK_SIZE == 0 || FEEDBACK_SIZE > BLOCK_SIZE || bits % 8 != 0)
throw Invalid_Argument(name + ": Invalid feedback size " +
to_string(bits));
}
}
/*************************************************
* CFB Encryption Constructor *
*************************************************/
CFB_Encryption::CFB_Encryption(const std::string& cipher_name,
u32bit fback_bits) :
BlockCipherMode(cipher_name, "CFB", block_size_of(cipher_name), 1),
FEEDBACK_SIZE(fback_bits ? fback_bits / 8: BLOCK_SIZE)
{
check_feedback(BLOCK_SIZE, FEEDBACK_SIZE, fback_bits, name());
}
/*************************************************
* CFB Encryption Constructor *
*************************************************/
CFB_Encryption::CFB_Encryption(const std::string& cipher_name,
const SymmetricKey& key,
const InitializationVector& iv,
u32bit fback_bits) :
BlockCipherMode(cipher_name, "CFB", block_size_of(cipher_name), 1),
FEEDBACK_SIZE(fback_bits ? fback_bits / 8: BLOCK_SIZE)
{
check_feedback(BLOCK_SIZE, FEEDBACK_SIZE, fback_bits, name());
set_key(key);
set_iv(iv);
}
/*************************************************
* Encrypt data in CFB mode *
*************************************************/
void CFB_Encryption::write(const byte input[], u32bit length)
{
while(length)
{
u32bit xored = std::min(FEEDBACK_SIZE - position, length);
xor_buf(buffer + position, input, xored);
send(buffer + position, xored);
input += xored;
length -= xored;
position += xored;
if(position == FEEDBACK_SIZE)
feedback();
}
}
/*************************************************
* Do the feedback *
*************************************************/
void CFB_Encryption::feedback()
{
for(u32bit j = 0; j != BLOCK_SIZE - FEEDBACK_SIZE; ++j)
state[j] = state[j + FEEDBACK_SIZE];
state.copy(BLOCK_SIZE - FEEDBACK_SIZE, buffer, FEEDBACK_SIZE);
cipher->encrypt(state, buffer);
position = 0;
}
/*************************************************
* CFB Decryption Constructor *
*************************************************/
CFB_Decryption::CFB_Decryption(const std::string& cipher_name,
u32bit fback_bits) :
BlockCipherMode(cipher_name, "CFB", block_size_of(cipher_name), 1),
FEEDBACK_SIZE(fback_bits ? fback_bits / 8 : BLOCK_SIZE)
{
check_feedback(BLOCK_SIZE, FEEDBACK_SIZE, fback_bits, name());
}
/*************************************************
* CFB Decryption Constructor *
*************************************************/
CFB_Decryption::CFB_Decryption(const std::string& cipher_name,
const SymmetricKey& key,
const InitializationVector& iv,
u32bit fback_bits) :
BlockCipherMode(cipher_name, "CFB", block_size_of(cipher_name), 1),
FEEDBACK_SIZE(fback_bits ? fback_bits / 8 : BLOCK_SIZE)
{
check_feedback(BLOCK_SIZE, FEEDBACK_SIZE, fback_bits, name());
set_key(key);
set_iv(iv);
}
/*************************************************
* Decrypt data in CFB mode *
*************************************************/
void CFB_Decryption::write(const byte input[], u32bit length)
{
while(length)
{
u32bit xored = std::min(FEEDBACK_SIZE - position, length);
xor_buf(buffer + position, input, xored);
send(buffer + position, xored);
buffer.copy(position, input, xored);
input += xored;
length -= xored;
position += xored;
if(position == FEEDBACK_SIZE)
feedback();
}
}
/*************************************************
* Do the feedback *
*************************************************/
void CFB_Decryption::feedback()
{
for(u32bit j = 0; j != BLOCK_SIZE - FEEDBACK_SIZE; ++j)
state[j] = state[j + FEEDBACK_SIZE];
state.copy(BLOCK_SIZE - FEEDBACK_SIZE, buffer, FEEDBACK_SIZE);
cipher->encrypt(state, buffer);
position = 0;
}
}
|
