Botan  2.12.1
Crypto and TLS for C++11
rc4.cpp
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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/rc4.h>
9 #include <botan/exceptn.h>
10 
11 namespace Botan {
12 
13 /*
14 * Combine cipher stream with message
15 */
16 void RC4::cipher(const uint8_t in[], uint8_t out[], size_t length)
17  {
18  verify_key_set(m_state.empty() == false);
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 
33  {
34  return new RC4(m_SKIP);
35  }
36 
38  {
39  return Key_Length_Specification(1, 256);
40  }
41 
42 void RC4::set_iv(const uint8_t*, size_t length)
43  {
44  if(length > 0)
45  throw Invalid_IV_Length("RC4", length);
46  }
47 
48 /*
49 * Generate cipher stream
50 */
51 void RC4::generate()
52  {
53  uint8_t SX, SY;
54  for(size_t i = 0; i != m_buffer.size(); i += 4)
55  {
56  SX = m_state[m_X+1]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
57  m_state[m_X+1] = SY; m_state[m_Y] = SX;
58  m_buffer[i] = m_state[(SX + SY) % 256];
59 
60  SX = m_state[m_X+2]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
61  m_state[m_X+2] = SY; m_state[m_Y] = SX;
62  m_buffer[i+1] = m_state[(SX + SY) % 256];
63 
64  SX = m_state[m_X+3]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
65  m_state[m_X+3] = SY; m_state[m_Y] = SX;
66  m_buffer[i+2] = m_state[(SX + SY) % 256];
67 
68  m_X = (m_X + 4) % 256;
69  SX = m_state[m_X]; m_Y = (m_Y + SX) % 256; SY = m_state[m_Y];
70  m_state[m_X] = SY; m_state[m_Y] = SX;
71  m_buffer[i+3] = m_state[(SX + SY) % 256];
72  }
73  m_position = 0;
74  }
75 
76 /*
77 * RC4 Key Schedule
78 */
79 void RC4::key_schedule(const uint8_t key[], size_t length)
80  {
81  m_state.resize(256);
82  m_buffer.resize(256);
83 
84  m_position = m_X = m_Y = 0;
85 
86  for(size_t i = 0; i != 256; ++i)
87  m_state[i] = static_cast<uint8_t>(i);
88 
89  for(size_t i = 0, state_index = 0; i != 256; ++i)
90  {
91  state_index = (state_index + key[i % length] + m_state[i]) % 256;
92  std::swap(m_state[i], m_state[state_index]);
93  }
94 
95  for(size_t i = 0; i <= m_SKIP; i += m_buffer.size())
96  generate();
97 
98  m_position += (m_SKIP % m_buffer.size());
99  }
100 
101 /*
102 * Return the name of this type
103 */
104 std::string RC4::name() const
105  {
106  if(m_SKIP == 0)
107  return "RC4";
108  else if(m_SKIP == 256)
109  return "MARK-4";
110  else
111  return "RC4(" + std::to_string(m_SKIP) + ")";
112  }
113 
114 /*
115 * Clear memory of sensitive data
116 */
118  {
119  zap(m_state);
120  zap(m_buffer);
121  m_position = m_X = m_Y = 0;
122  }
123 
124 /*
125 * RC4 Constructor
126 */
127 RC4::RC4(size_t s) : m_SKIP(s) {}
128 
129 void RC4::seek(uint64_t)
130  {
131  throw Not_Implemented("RC4 does not support seeking");
132  }
133 }
void clear() override
Definition: rc4.cpp:117
StreamCipher * clone() const override
Definition: rc4.cpp:32
void verify_key_set(bool cond) const
Definition: sym_algo.h:89
void zap(std::vector< T, Alloc > &vec)
Definition: secmem.h:170
Key_Length_Specification key_spec() const override
Definition: rc4.cpp:37
std::string to_string(const BER_Object &obj)
Definition: asn1_obj.cpp:213
void seek(uint64_t offset) override
Definition: rc4.cpp:129
void xor_buf(uint8_t out[], const uint8_t in[], size_t length)
Definition: mem_ops.h:207
void cipher(const uint8_t in[], uint8_t out[], size_t length) override
Definition: rc4.cpp:16
Definition: alg_id.cpp:13
std::string name() const override
Definition: rc4.cpp:104
void set_iv(const uint8_t iv[], size_t iv_len) override
Definition: rc4.cpp:42
RC4(size_t skip=0)
Definition: rc4.cpp:127