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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
/*
* DSA
* (C) 1999-2010,2014,2016 Jack Lloyd
* (C) 2016 René Korthaus
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/dsa.h>
#include <botan/keypair.h>
#include <botan/reducer.h>
#include <botan/rng.h>
#include <botan/internal/pk_ops_impl.h>
#if defined(BOTAN_HAS_RFC6979_GENERATOR)
#include <botan/emsa.h>
#include <botan/rfc6979.h>
#endif
namespace Botan {
/*
* DSA_PublicKey Constructor
*/
DSA_PublicKey::DSA_PublicKey(const DL_Group& grp, const BigInt& y1)
{
m_group = grp;
m_y = y1;
}
/*
* Create a DSA private key
*/
DSA_PrivateKey::DSA_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
m_group = grp;
if(x_arg == 0)
m_x = BigInt::random_integer(rng, 2, group_q());
else
m_x = x_arg;
m_y = m_group.power_g_p(m_x, m_group.q_bits());
}
DSA_PrivateKey::DSA_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<uint8_t>& key_bits) :
DL_Scheme_PrivateKey(alg_id, key_bits, DL_Group::ANSI_X9_57)
{
m_y = m_group.power_g_p(m_x, m_group.q_bits());
}
/*
* Check Private DSA Parameters
*/
bool DSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
{
if(!DL_Scheme_PrivateKey::check_key(rng, strong) || m_x >= group_q())
return false;
if(!strong)
return true;
return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-256)");
}
namespace {
/**
* Object that can create a DSA signature
*/
class DSA_Signature_Operation final : public PK_Ops::Signature_with_EMSA
{
public:
DSA_Signature_Operation(const DSA_PrivateKey& dsa,
const std::string& emsa,
RandomNumberGenerator& rng) :
PK_Ops::Signature_with_EMSA(emsa),
m_group(dsa.get_group()),
m_x(dsa.get_x())
{
#if defined(BOTAN_HAS_RFC6979_GENERATOR)
m_rfc6979_hash = hash_for_emsa(emsa);
#endif
m_b = BigInt::random_integer(rng, 2, dsa.group_q());
m_b_inv = m_group.inverse_mod_q(m_b);
}
size_t signature_length() const override { return 2*m_group.q_bytes(); }
size_t max_input_bits() const override { return m_group.q_bits(); }
secure_vector<uint8_t> raw_sign(const uint8_t msg[], size_t msg_len,
RandomNumberGenerator& rng) override;
private:
const DL_Group m_group;
const BigInt& m_x;
#if defined(BOTAN_HAS_RFC6979_GENERATOR)
std::string m_rfc6979_hash;
#endif
BigInt m_b, m_b_inv;
};
secure_vector<uint8_t>
DSA_Signature_Operation::raw_sign(const uint8_t msg[], size_t msg_len,
RandomNumberGenerator& rng)
{
const BigInt& q = m_group.get_q();
BigInt m(msg, msg_len, m_group.q_bits());
while(m >= q)
m -= q;
#if defined(BOTAN_HAS_RFC6979_GENERATOR)
BOTAN_UNUSED(rng);
const BigInt k = generate_rfc6979_nonce(m_x, q, m, m_rfc6979_hash);
#else
const BigInt k = BigInt::random_integer(rng, 1, q);
#endif
const BigInt k_inv = m_group.inverse_mod_q(k);
const BigInt r = m_group.mod_q(m_group.power_g_p(k, m_group.q_bits()));
/*
* Blind the input message and compute x*r+m as (x*r*b + m*b)/b
*/
m_b = m_group.square_mod_q(m_b);
m_b_inv = m_group.square_mod_q(m_b_inv);
m = m_group.multiply_mod_q(m_b, m);
const BigInt xr = m_group.multiply_mod_q(m_b, m_x, r);
const BigInt s = m_group.multiply_mod_q(m_b_inv, k_inv, m_group.mod_q(xr+m));
// With overwhelming probability, a bug rather than actual zero r/s
if(r.is_zero() || s.is_zero())
throw Internal_Error("Computed zero r/s during DSA signature");
return BigInt::encode_fixed_length_int_pair(r, s, q.bytes());
}
/**
* Object that can verify a DSA signature
*/
class DSA_Verification_Operation final : public PK_Ops::Verification_with_EMSA
{
public:
DSA_Verification_Operation(const DSA_PublicKey& dsa,
const std::string& emsa) :
PK_Ops::Verification_with_EMSA(emsa),
m_group(dsa.get_group()),
m_y(dsa.get_y())
{
}
size_t max_input_bits() const override { return m_group.q_bits(); }
bool with_recovery() const override { return false; }
bool verify(const uint8_t msg[], size_t msg_len,
const uint8_t sig[], size_t sig_len) override;
private:
const DL_Group m_group;
const BigInt& m_y;
};
bool DSA_Verification_Operation::verify(const uint8_t msg[], size_t msg_len,
const uint8_t sig[], size_t sig_len)
{
const BigInt& q = m_group.get_q();
const size_t q_bytes = q.bytes();
if(sig_len != 2*q_bytes || msg_len > q_bytes)
return false;
BigInt r(sig, q_bytes);
BigInt s(sig + q_bytes, q_bytes);
BigInt i(msg, msg_len, q.bits());
if(r <= 0 || r >= q || s <= 0 || s >= q)
return false;
s = inverse_mod(s, q);
const BigInt sr = m_group.multiply_mod_q(s, r);
const BigInt si = m_group.multiply_mod_q(s, i);
s = m_group.multi_exponentiate(si, m_y, sr);
return (m_group.mod_q(s) == r);
}
}
std::unique_ptr<PK_Ops::Verification>
DSA_PublicKey::create_verification_op(const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
return std::unique_ptr<PK_Ops::Verification>(new DSA_Verification_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
std::unique_ptr<PK_Ops::Signature>
DSA_PrivateKey::create_signature_op(RandomNumberGenerator& rng,
const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
return std::unique_ptr<PK_Ops::Signature>(new DSA_Signature_Operation(*this, params, rng));
throw Provider_Not_Found(algo_name(), provider);
}
}
|
