Botan 2.19.1
Crypto and TLS for C&
eckcdsa.cpp
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1/*
2* ECKCDSA (ISO/IEC 14888-3:2006/Cor.2:2009)
3* (C) 2016 René Korthaus, Sirrix AG
4* (C) 2018 Jack Lloyd
5*
6* Botan is released under the Simplified BSD License (see license.txt)
7*/
8
9#include <botan/eckcdsa.h>
10#include <botan/internal/pk_ops_impl.h>
11#include <botan/internal/point_mul.h>
12#include <botan/keypair.h>
13#include <botan/reducer.h>
14#include <botan/emsa.h>
15#include <botan/hash.h>
16#include <botan/rng.h>
17
18namespace Botan {
19
21 bool strong) const
22 {
23 if(!public_point().on_the_curve())
24 {
25 return false;
26 }
27
28 if(!strong)
29 {
30 return true;
31 }
32
33 return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-256)");
34 }
35
36namespace {
37
38/**
39* ECKCDSA signature operation
40*/
41class ECKCDSA_Signature_Operation final : public PK_Ops::Signature_with_EMSA
42 {
43 public:
44
45 ECKCDSA_Signature_Operation(const ECKCDSA_PrivateKey& eckcdsa,
46 const std::string& emsa) :
47 PK_Ops::Signature_with_EMSA(emsa),
48 m_group(eckcdsa.domain()),
49 m_x(eckcdsa.private_value()),
50 m_prefix()
51 {
52 const BigInt public_point_x = eckcdsa.public_point().get_affine_x();
53 const BigInt public_point_y = eckcdsa.public_point().get_affine_y();
54
55 m_prefix.resize(public_point_x.bytes() + public_point_y.bytes());
56 public_point_x.binary_encode(m_prefix.data());
57 public_point_y.binary_encode(&m_prefix[public_point_x.bytes()]);
58 m_prefix.resize(HashFunction::create(hash_for_signature())->hash_block_size()); // use only the "hash input block size" leftmost bits
59 }
60
61 secure_vector<uint8_t> raw_sign(const uint8_t msg[], size_t msg_len,
62 RandomNumberGenerator& rng) override;
63
64 size_t signature_length() const override { return 2*m_group.get_order_bytes(); }
65 size_t max_input_bits() const override { return m_group.get_order_bits(); }
66
67 bool has_prefix() override { return true; }
68 secure_vector<uint8_t> message_prefix() const override { return m_prefix; }
69
70 private:
71 const EC_Group m_group;
72 const BigInt& m_x;
73 secure_vector<uint8_t> m_prefix;
74 std::vector<BigInt> m_ws;
75 };
76
77secure_vector<uint8_t>
78ECKCDSA_Signature_Operation::raw_sign(const uint8_t msg[], size_t,
79 RandomNumberGenerator& rng)
80 {
81 const BigInt k = m_group.random_scalar(rng);
82 const BigInt k_times_P_x = m_group.blinded_base_point_multiply_x(k, rng, m_ws);
83
84 secure_vector<uint8_t> to_be_hashed(k_times_P_x.bytes());
85 k_times_P_x.binary_encode(to_be_hashed.data());
86
87 std::unique_ptr<EMSA> emsa = this->clone_emsa();
88 emsa->update(to_be_hashed.data(), to_be_hashed.size());
89 secure_vector<uint8_t> c = emsa->raw_data();
90 c = emsa->encoding_of(c, max_input_bits(), rng);
91
92 const BigInt r(c.data(), c.size());
93
94 xor_buf(c, msg, c.size());
95 BigInt w(c.data(), c.size());
96 w = m_group.mod_order(w);
97
98 const BigInt s = m_group.multiply_mod_order(m_x, k - w);
99 if(s.is_zero())
100 throw Internal_Error("During ECKCDSA signature generation created zero s");
101
102 secure_vector<uint8_t> output = BigInt::encode_1363(r, c.size());
103 output += BigInt::encode_1363(s, m_group.get_order_bytes());
104 return output;
105 }
106
107/**
108* ECKCDSA verification operation
109*/
110class ECKCDSA_Verification_Operation final : public PK_Ops::Verification_with_EMSA
111 {
112 public:
113
114 ECKCDSA_Verification_Operation(const ECKCDSA_PublicKey& eckcdsa,
115 const std::string& emsa) :
116 PK_Ops::Verification_with_EMSA(emsa),
117 m_group(eckcdsa.domain()),
118 m_gy_mul(m_group.get_base_point(), eckcdsa.public_point()),
119 m_prefix()
120 {
121 const BigInt public_point_x = eckcdsa.public_point().get_affine_x();
122 const BigInt public_point_y = eckcdsa.public_point().get_affine_y();
123
124 m_prefix.resize(public_point_x.bytes() + public_point_y.bytes());
125 public_point_x.binary_encode(&m_prefix[0]);
126 public_point_y.binary_encode(&m_prefix[public_point_x.bytes()]);
127 m_prefix.resize(HashFunction::create(hash_for_signature())->hash_block_size()); // use only the "hash input block size" leftmost bits
128 }
129
130 bool has_prefix() override { return true; }
131 secure_vector<uint8_t> message_prefix() const override { return m_prefix; }
132
133 size_t max_input_bits() const override { return m_group.get_order_bits(); }
134
135 bool with_recovery() const override { return false; }
136
137 bool verify(const uint8_t msg[], size_t msg_len,
138 const uint8_t sig[], size_t sig_len) override;
139 private:
140 const EC_Group m_group;
141 const PointGFp_Multi_Point_Precompute m_gy_mul;
142 secure_vector<uint8_t> m_prefix;
143 };
144
145bool ECKCDSA_Verification_Operation::verify(const uint8_t msg[], size_t,
146 const uint8_t sig[], size_t sig_len)
147 {
148 const std::unique_ptr<HashFunction> hash = HashFunction::create(hash_for_signature());
149 //calculate size of r
150
151 const size_t order_bytes = m_group.get_order_bytes();
152
153 const size_t size_r = std::min(hash -> output_length(), order_bytes);
154 if(sig_len != size_r + order_bytes)
155 {
156 return false;
157 }
158
159 secure_vector<uint8_t> r(sig, sig + size_r);
160
161 // check that 0 < s < q
162 const BigInt s(sig + size_r, order_bytes);
163
164 if(s <= 0 || s >= m_group.get_order())
165 {
166 return false;
167 }
168
169 secure_vector<uint8_t> r_xor_e(r);
170 xor_buf(r_xor_e, msg, r.size());
171 BigInt w(r_xor_e.data(), r_xor_e.size());
172 w = m_group.mod_order(w);
173
174 const PointGFp q = m_gy_mul.multi_exp(w, s);
175 const BigInt q_x = q.get_affine_x();
176 secure_vector<uint8_t> c(q_x.bytes());
177 q_x.binary_encode(c.data());
178 std::unique_ptr<EMSA> emsa = this->clone_emsa();
179 emsa->update(c.data(), c.size());
180 secure_vector<uint8_t> v = emsa->raw_data();
181 Null_RNG rng;
182 v = emsa->encoding_of(v, max_input_bits(), rng);
183
184 return (v == r);
185 }
186
187}
188
189std::unique_ptr<PK_Ops::Verification>
191 const std::string& provider) const
192 {
193 if(provider == "base" || provider.empty())
194 return std::unique_ptr<PK_Ops::Verification>(new ECKCDSA_Verification_Operation(*this, params));
195 throw Provider_Not_Found(algo_name(), provider);
196 }
197
198std::unique_ptr<PK_Ops::Signature>
200 const std::string& params,
201 const std::string& provider) const
202 {
203 if(provider == "base" || provider.empty())
204 return std::unique_ptr<PK_Ops::Signature>(new ECKCDSA_Signature_Operation(*this, params));
205 throw Provider_Not_Found(algo_name(), provider);
206 }
207
208}
void binary_encode(uint8_t buf[]) const
Definition: bigint.cpp:399
static secure_vector< uint8_t > encode_1363(const BigInt &n, size_t bytes)
Definition: big_code.cpp:111
size_t bytes() const
Definition: bigint.cpp:281
std::unique_ptr< PK_Ops::Signature > create_signature_op(RandomNumberGenerator &rng, const std::string &params, const std::string &provider) const override
Definition: eckcdsa.cpp:199
bool check_key(RandomNumberGenerator &rng, bool) const override
Definition: eckcdsa.cpp:20
std::string algo_name() const override
Definition: eckcdsa.h:44
std::unique_ptr< PK_Ops::Verification > create_verification_op(const std::string &params, const std::string &provider) const override
Definition: eckcdsa.cpp:190
const PointGFp & public_point() const
Definition: ecc_key.h:57
static std::unique_ptr< HashFunction > create(const std::string &algo_spec, const std::string &provider="")
Definition: hash.cpp:106
PointGFp multi_exp(const BigInt &k1, const BigInt &k2) const
Definition: point_mul.cpp:394
BigInt get_affine_y() const
Definition: point_gfp.cpp:524
BigInt get_affine_x() const
Definition: point_gfp.cpp:505
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
void xor_buf(uint8_t out[], const uint8_t in[], size_t length)
Definition: mem_ops.h:262
MechanismType hash