Botan  2.6.0
Crypto and TLS for C++11
emsa_x931.cpp
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1 /*
2 * EMSA_X931
3 * (C) 1999-2007 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/emsa_x931.h>
9 #include <botan/exceptn.h>
10 #include <botan/hash_id.h>
11 
12 namespace Botan {
13 
14 namespace {
15 
16 secure_vector<uint8_t> emsa2_encoding(const secure_vector<uint8_t>& msg,
17  size_t output_bits,
18  const secure_vector<uint8_t>& empty_hash,
19  uint8_t hash_id)
20  {
21  const size_t HASH_SIZE = empty_hash.size();
22 
23  size_t output_length = (output_bits + 1) / 8;
24 
25  if(msg.size() != HASH_SIZE)
26  throw Encoding_Error("EMSA_X931::encoding_of: Bad input length");
27  if(output_length < HASH_SIZE + 4)
28  throw Encoding_Error("EMSA_X931::encoding_of: Output length is too small");
29 
30  const bool empty_input = (msg == empty_hash);
31 
32  secure_vector<uint8_t> output(output_length);
33 
34  output[0] = (empty_input ? 0x4B : 0x6B);
35  output[output_length - 3 - HASH_SIZE] = 0xBA;
36  set_mem(&output[1], output_length - 4 - HASH_SIZE, 0xBB);
37  buffer_insert(output, output_length - (HASH_SIZE + 2), msg.data(), msg.size());
38  output[output_length-2] = hash_id;
39  output[output_length-1] = 0xCC;
40 
41  return output;
42  }
43 
44 }
45 
46 std::string EMSA_X931::name() const
47  {
48  return "EMSA2(" + m_hash->name() + ")";
49  }
50 
51 void EMSA_X931::update(const uint8_t input[], size_t length)
52  {
53  m_hash->update(input, length);
54  }
55 
56 secure_vector<uint8_t> EMSA_X931::raw_data()
57  {
58  return m_hash->final();
59  }
60 
61 /*
62 * EMSA_X931 Encode Operation
63 */
64 secure_vector<uint8_t> EMSA_X931::encoding_of(const secure_vector<uint8_t>& msg,
65  size_t output_bits,
66  RandomNumberGenerator&)
67  {
68  return emsa2_encoding(msg, output_bits, m_empty_hash, m_hash_id);
69  }
70 
71 /*
72 * EMSA_X931 Verify Operation
73 */
74 bool EMSA_X931::verify(const secure_vector<uint8_t>& coded,
75  const secure_vector<uint8_t>& raw,
76  size_t key_bits)
77  {
78  try
79  {
80  return (coded == emsa2_encoding(raw, key_bits,
81  m_empty_hash, m_hash_id));
82  }
83  catch(...)
84  {
85  return false;
86  }
87  }
88 
89 /*
90 * EMSA_X931 Constructor
91 */
93  {
94  m_empty_hash = m_hash->final();
95 
96  m_hash_id = ieee1363_hash_id(hash->name());
97 
98  if(!m_hash_id)
99  throw Encoding_Error("EMSA_X931 no hash identifier for " + hash->name());
100  }
101 
102 }
uint8_t ieee1363_hash_id(const std::string &name)
Definition: hash_id.cpp:146
void set_mem(T *ptr, size_t n, uint8_t val)
Definition: mem_ops.h:123
std::string name() const override
Definition: emsa_x931.cpp:46
Definition: alg_id.cpp:13
EMSA_X931(HashFunction *hash)
Definition: emsa_x931.cpp:92
size_t buffer_insert(std::vector< T, Alloc > &buf, size_t buf_offset, const T input[], size_t input_length)
Definition: secmem.h:103
MechanismType hash