Botan  2.1.0
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/hash_id.h>
10 
11 namespace Botan {
12 
13 namespace {
14 
15 secure_vector<uint8_t> emsa2_encoding(const secure_vector<uint8_t>& msg,
16  size_t output_bits,
17  const secure_vector<uint8_t>& empty_hash,
18  uint8_t hash_id)
19  {
20  const size_t HASH_SIZE = empty_hash.size();
21 
22  size_t output_length = (output_bits + 1) / 8;
23 
24  if(msg.size() != HASH_SIZE)
25  throw Encoding_Error("EMSA_X931::encoding_of: Bad input length");
26  if(output_length < HASH_SIZE + 4)
27  throw Encoding_Error("EMSA_X931::encoding_of: Output length is too small");
28 
29  const bool empty_input = (msg == empty_hash);
30 
31  secure_vector<uint8_t> output(output_length);
32 
33  output[0] = (empty_input ? 0x4B : 0x6B);
34  output[output_length - 3 - HASH_SIZE] = 0xBA;
35  set_mem(&output[1], output_length - 4 - HASH_SIZE, 0xBB);
36  buffer_insert(output, output_length - (HASH_SIZE + 2), msg.data(), msg.size());
37  output[output_length-2] = hash_id;
38  output[output_length-1] = 0xCC;
39 
40  return output;
41  }
42 
43 }
44 
45 void EMSA_X931::update(const uint8_t input[], size_t length)
46  {
47  m_hash->update(input, length);
48  }
49 
50 secure_vector<uint8_t> EMSA_X931::raw_data()
51  {
52  return m_hash->final();
53  }
54 
55 /*
56 * EMSA_X931 Encode Operation
57 */
58 secure_vector<uint8_t> EMSA_X931::encoding_of(const secure_vector<uint8_t>& msg,
59  size_t output_bits,
60  RandomNumberGenerator&)
61  {
62  return emsa2_encoding(msg, output_bits, m_empty_hash, m_hash_id);
63  }
64 
65 /*
66 * EMSA_X931 Verify Operation
67 */
68 bool EMSA_X931::verify(const secure_vector<uint8_t>& coded,
69  const secure_vector<uint8_t>& raw,
70  size_t key_bits)
71  {
72  try
73  {
74  return (coded == emsa2_encoding(raw, key_bits,
75  m_empty_hash, m_hash_id));
76  }
77  catch(...)
78  {
79  return false;
80  }
81  }
82 
83 /*
84 * EMSA_X931 Constructor
85 */
87  {
88  m_empty_hash = m_hash->final();
89 
90  m_hash_id = ieee1363_hash_id(hash->name());
91 
92  if(!m_hash_id)
93  throw Encoding_Error("EMSA_X931 no hash identifier for " + hash->name());
94  }
95 
96 }
virtual std::string name() const =0
uint8_t ieee1363_hash_id(const std::string &name)
Definition: hash_id.cpp:104
void set_mem(T *ptr, size_t n, uint8_t val)
Definition: mem_ops.h:83
Definition: alg_id.cpp:13
EMSA_X931(HashFunction *hash)
Definition: emsa_x931.cpp:86
size_t buffer_insert(std::vector< T, Alloc > &buf, size_t buf_offset, const T input[], size_t input_length)
Definition: secmem.h:133
std::unique_ptr< HashFunction > m_hash
Definition: tpm.cpp:439
MechanismType hash