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
|
/*
* RC4
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/rc4.h>
#include <botan/exceptn.h>
namespace Botan {
/*
* Combine cipher stream with message
*/
void RC4::cipher(const uint8_t in[], uint8_t out[], size_t length)
{
verify_key_set(m_state.empty() == false);
while(length >= m_buffer.size() - m_position)
{
xor_buf(out, in, &m_buffer[m_position], m_buffer.size() - m_position);
length -= (m_buffer.size() - m_position);
in += (m_buffer.size() - m_position);
out += (m_buffer.size() - m_position);
generate();
}
xor_buf(out, in, &m_buffer[m_position], length);
m_position += length;
}
StreamCipher* RC4::clone() const
{
return new RC4(m_SKIP);
}
Key_Length_Specification RC4::key_spec() const
{
return Key_Length_Specification(1, 256);
}
void RC4::set_iv(const uint8_t*, size_t length)
{
if(length > 0)
throw Invalid_IV_Length("RC4", length);
}
/*
* Generate cipher stream
*/
void RC4::generate()
{
uint8_t SX, SY;
for(size_t i = 0; i != m_buffer.size(); i += 4)
{
SX = m_state[m_X+1]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
m_state[m_X+1] = SY; m_state[m_Y] = SX;
m_buffer[i] = m_state[(SX + SY) % 256];
SX = m_state[m_X+2]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
m_state[m_X+2] = SY; m_state[m_Y] = SX;
m_buffer[i+1] = m_state[(SX + SY) % 256];
SX = m_state[m_X+3]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
m_state[m_X+3] = SY; m_state[m_Y] = SX;
m_buffer[i+2] = m_state[(SX + SY) % 256];
m_X = (m_X + 4) % 256;
SX = m_state[m_X]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
m_state[m_X] = SY; m_state[m_Y] = SX;
m_buffer[i+3] = m_state[(SX + SY) % 256];
}
m_position = 0;
}
/*
* RC4 Key Schedule
*/
void RC4::key_schedule(const uint8_t key[], size_t length)
{
m_state.resize(256);
m_buffer.resize(256);
m_position = m_X = m_Y = 0;
for(size_t i = 0; i != 256; ++i)
m_state[i] = static_cast<uint8_t>(i);
for(size_t i = 0, state_index = 0; i != 256; ++i)
{
state_index = (state_index + key[i % length] + m_state[i]) % 256;
std::swap(m_state[i], m_state[state_index]);
}
for(size_t i = 0; i <= m_SKIP; i += m_buffer.size())
generate();
m_position += (m_SKIP % m_buffer.size());
}
/*
* Return the name of this type
*/
std::string RC4::name() const
{
if(m_SKIP == 0)
return "RC4";
else if(m_SKIP == 256)
return "MARK-4";
else
return "RC4(" + std::to_string(m_SKIP) + ")";
}
/*
* Clear memory of sensitive data
*/
void RC4::clear()
{
zap(m_state);
zap(m_buffer);
m_position = m_X = m_Y = 0;
}
/*
* RC4 Constructor
*/
RC4::RC4(size_t s) : m_SKIP(s) {}
void RC4::seek(uint64_t)
{
throw Not_Implemented("RC4 does not support seeking");
}
}
|
