Botan 2.19.1
Crypto and TLS for C&
ecgdsa.cpp
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1/*
2* ECGDSA (BSI-TR-03111, version 2.0)
3* (C) 2016 René Korthaus
4* (C) 2018 Jack Lloyd
5*
6* Botan is released under the Simplified BSD License (see license.txt)
7*/
8
9#include <botan/ecgdsa.h>
10#include <botan/keypair.h>
11#include <botan/reducer.h>
12#include <botan/internal/pk_ops_impl.h>
13#include <botan/internal/point_mul.h>
14
15namespace Botan {
16
18 bool strong) const
19 {
20 if(!public_point().on_the_curve())
21 return false;
22
23 if(!strong)
24 return true;
25
26 return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-256)");
27 }
28
29namespace {
30
31/**
32* ECGDSA signature operation
33*/
34class ECGDSA_Signature_Operation final : public PK_Ops::Signature_with_EMSA
35 {
36 public:
37
38 ECGDSA_Signature_Operation(const ECGDSA_PrivateKey& ecgdsa,
39 const std::string& emsa) :
40 PK_Ops::Signature_with_EMSA(emsa),
41 m_group(ecgdsa.domain()),
42 m_x(ecgdsa.private_value())
43 {
44 }
45
46 secure_vector<uint8_t> raw_sign(const uint8_t msg[], size_t msg_len,
47 RandomNumberGenerator& rng) override;
48
49 size_t signature_length() const override { return 2*m_group.get_order_bytes(); }
50
51 size_t max_input_bits() const override { return m_group.get_order_bits(); }
52
53 private:
54 const EC_Group m_group;
55 const BigInt& m_x;
56 std::vector<BigInt> m_ws;
57 };
58
59secure_vector<uint8_t>
60ECGDSA_Signature_Operation::raw_sign(const uint8_t msg[], size_t msg_len,
61 RandomNumberGenerator& rng)
62 {
63 const BigInt m(msg, msg_len, m_group.get_order_bits());
64
65 const BigInt k = m_group.random_scalar(rng);
66
67 const BigInt r = m_group.mod_order(
68 m_group.blinded_base_point_multiply_x(k, rng, m_ws));
69
70 const BigInt kr = m_group.multiply_mod_order(k, r);
71
72 const BigInt s = m_group.multiply_mod_order(m_x, kr - m);
73
74 // With overwhelming probability, a bug rather than actual zero r/s
75 if(r.is_zero() || s.is_zero())
76 throw Internal_Error("During ECGDSA signature generated zero r/s");
77
78 return BigInt::encode_fixed_length_int_pair(r, s, m_group.get_order_bytes());
79 }
80
81/**
82* ECGDSA verification operation
83*/
84class ECGDSA_Verification_Operation final : public PK_Ops::Verification_with_EMSA
85 {
86 public:
87
88 ECGDSA_Verification_Operation(const ECGDSA_PublicKey& ecgdsa,
89 const std::string& emsa) :
90 PK_Ops::Verification_with_EMSA(emsa),
91 m_group(ecgdsa.domain()),
92 m_gy_mul(m_group.get_base_point(), ecgdsa.public_point())
93 {
94 }
95
96 size_t max_input_bits() const override { return m_group.get_order_bits(); }
97
98 bool with_recovery() const override { return false; }
99
100 bool verify(const uint8_t msg[], size_t msg_len,
101 const uint8_t sig[], size_t sig_len) override;
102 private:
103 const EC_Group m_group;
104 const PointGFp_Multi_Point_Precompute m_gy_mul;
105 };
106
107bool ECGDSA_Verification_Operation::verify(const uint8_t msg[], size_t msg_len,
108 const uint8_t sig[], size_t sig_len)
109 {
110 if(sig_len != m_group.get_order_bytes() * 2)
111 return false;
112
113 const BigInt e(msg, msg_len, m_group.get_order_bits());
114
115 const BigInt r(sig, sig_len / 2);
116 const BigInt s(sig + sig_len / 2, sig_len / 2);
117
118 if(r <= 0 || r >= m_group.get_order() || s <= 0 || s >= m_group.get_order())
119 return false;
120
121 const BigInt w = m_group.inverse_mod_order(r);
122
123 const BigInt u1 = m_group.multiply_mod_order(e, w);
124 const BigInt u2 = m_group.multiply_mod_order(s, w);
125 const PointGFp R = m_gy_mul.multi_exp(u1, u2);
126
127 if(R.is_zero())
128 return false;
129
130 const BigInt v = m_group.mod_order(R.get_affine_x());
131 return (v == r);
132 }
133
134}
135
136std::unique_ptr<PK_Ops::Verification>
138 const std::string& provider) const
139 {
140 if(provider == "base" || provider.empty())
141 return std::unique_ptr<PK_Ops::Verification>(new ECGDSA_Verification_Operation(*this, params));
142 throw Provider_Not_Found(algo_name(), provider);
143 }
144
145std::unique_ptr<PK_Ops::Signature>
147 const std::string& params,
148 const std::string& provider) const
149 {
150 if(provider == "base" || provider.empty())
151 return std::unique_ptr<PK_Ops::Signature>(new ECGDSA_Signature_Operation(*this, params));
152 throw Provider_Not_Found(algo_name(), provider);
153 }
154
155}
static secure_vector< uint8_t > encode_fixed_length_int_pair(const BigInt &n1, const BigInt &n2, size_t bytes)
Definition: big_code.cpp:133
std::unique_ptr< PK_Ops::Signature > create_signature_op(RandomNumberGenerator &rng, const std::string &params, const std::string &provider) const override
Definition: ecgdsa.cpp:146
bool check_key(RandomNumberGenerator &rng, bool) const override
Definition: ecgdsa.cpp:17
std::string algo_name() const override
Definition: ecgdsa.h:44
std::unique_ptr< PK_Ops::Verification > create_verification_op(const std::string &params, const std::string &provider) const override
Definition: ecgdsa.cpp:137
const PointGFp & public_point() const
Definition: ecc_key.h:57
PointGFp multi_exp(const BigInt &k1, const BigInt &k2) const
Definition: point_mul.cpp:394
int(* final)(unsigned char *, CTX *)
bool signature_consistency_check(RandomNumberGenerator &rng, const Private_Key &private_key, const Public_Key &public_key, const std::string &padding)
Definition: keypair.cpp:49
Definition: alg_id.cpp:13