Botan 3.0.0
Crypto and TLS for C&
rc4.cpp
Go to the documentation of this file.
1/*
2* RC4
3* (C) 1999-2007 Jack Lloyd
4*
5* Botan is released under the Simplified BSD License (see license.txt)
6*/
7
8#include <botan/internal/rc4.h>
9#include <botan/exceptn.h>
10
11namespace Botan {
12
13/*
14* Combine cipher stream with message
15*/
16void RC4::cipher_bytes(const uint8_t in[], uint8_t out[], size_t length)
17 {
19
20 while(length >= m_buffer.size() - m_position)
21 {
22 xor_buf(out, in, &m_buffer[m_position], m_buffer.size() - m_position);
23 length -= (m_buffer.size() - m_position);
24 in += (m_buffer.size() - m_position);
25 out += (m_buffer.size() - m_position);
26 generate();
27 }
28 xor_buf(out, in, &m_buffer[m_position], length);
29 m_position += length;
30 }
31
32std::unique_ptr<StreamCipher> RC4::new_object() const
33 {
34 return std::make_unique<RC4>(m_SKIP);
35 }
36
37size_t RC4::buffer_size() const
38 {
39 return 256;
40 }
41
43 {
44 return Key_Length_Specification(1, 256);
45 }
46
47void RC4::set_iv_bytes(const uint8_t* /*iv*/, size_t length)
48 {
49 if(length > 0)
50 throw Invalid_IV_Length("RC4", length);
51 }
52
53/*
54* Generate cipher stream
55*/
56void RC4::generate()
57 {
58 uint8_t SX, SY;
59 for(size_t i = 0; i != m_buffer.size(); i += 4)
60 {
61 SX = m_state[m_X+1]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
62 m_state[m_X+1] = SY; m_state[m_Y] = SX;
63 m_buffer[i] = m_state[(SX + SY) % 256];
64
65 SX = m_state[m_X+2]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
66 m_state[m_X+2] = SY; m_state[m_Y] = SX;
67 m_buffer[i+1] = m_state[(SX + SY) % 256];
68
69 SX = m_state[m_X+3]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
70 m_state[m_X+3] = SY; m_state[m_Y] = SX;
71 m_buffer[i+2] = m_state[(SX + SY) % 256];
72
73 m_X = (m_X + 4) % 256;
74 SX = m_state[m_X]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
75 m_state[m_X] = SY; m_state[m_Y] = SX;
76 m_buffer[i+3] = m_state[(SX + SY) % 256];
77 }
78 m_position = 0;
79 }
80
82 {
83 return !m_state.empty();
84 }
85
86/*
87* RC4 Key Schedule
88*/
89void RC4::key_schedule(const uint8_t key[], size_t length)
90 {
91 m_state.resize(256);
92 m_buffer.resize(256);
93
94 m_position = m_X = m_Y = 0;
95
96 for(size_t i = 0; i != 256; ++i)
97 m_state[i] = static_cast<uint8_t>(i);
98
99 for(size_t i = 0, state_index = 0; i != 256; ++i)
100 {
101 state_index = (state_index + key[i % length] + m_state[i]) % 256;
102 std::swap(m_state[i], m_state[state_index]);
103 }
104
105 for(size_t i = 0; i <= m_SKIP; i += m_buffer.size())
106 generate();
107
108 m_position += (m_SKIP % m_buffer.size());
109 }
110
111/*
112* Return the name of this type
113*/
114std::string RC4::name() const
115 {
116 if(m_SKIP == 0)
117 return "RC4";
118 else if(m_SKIP == 256)
119 return "MARK-4";
120 else
121 return "RC4(" + std::to_string(m_SKIP) + ")";
122 }
123
124/*
125* Clear memory of sensitive data
126*/
128 {
129 zap(m_state);
130 zap(m_buffer);
131 m_position = m_X = m_Y = 0;
132 }
133
134/*
135* RC4 Constructor
136*/
137RC4::RC4(size_t s) : m_SKIP(s) {}
138
139void RC4::seek(uint64_t /*offset*/)
140 {
141 throw Not_Implemented("RC4 does not support seeking");
142 }
143}
Key_Length_Specification key_spec() const override
Definition: rc4.cpp:42
std::string name() const override
Definition: rc4.cpp:114
std::unique_ptr< StreamCipher > new_object() const override
Definition: rc4.cpp:32
void clear() override
Definition: rc4.cpp:127
RC4(size_t skip=0)
Definition: rc4.cpp:137
size_t buffer_size() const override
Definition: rc4.cpp:37
void seek(uint64_t offset) override
Definition: rc4.cpp:139
bool has_keying_material() const override
Definition: rc4.cpp:81
void assert_key_material_set() const
Definition: sym_algo.h:182
Definition: alg_id.cpp:12
void zap(std::vector< T, Alloc > &vec)
Definition: secmem.h:129
void xor_buf(uint8_t out[], const uint8_t in[], size_t length)
Definition: mem_ops.h:255