Botan: src/pubkey/ecdsa/ecdsa.cpp Source File

Botan 1.10.16

ecdsa.cpp
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1 /*
2 * ECDSA implemenation
3 * (C) 2007 Manuel Hartl, FlexSecure GmbH
4 * 2007 Falko Strenzke, FlexSecure GmbH
5 * 2008-2010 Jack Lloyd
6 *
7 * Distributed under the terms of the Botan license
8 */
9
10 #include <botan/ecdsa.h>
11 #include <botan/keypair.h>
12
13 namespace Botan {
14
15 bool ECDSA_PrivateKey::check_key(RandomNumberGenerator& rng,
16 bool strong) const
17 {
18 if(!public_point().on_the_curve())
19 return false;
20
21 if(!strong)
22 return true;
23
24 return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-1)");
25 }
26
27 ECDSA_Signature_Operation::ECDSA_Signature_Operation(const ECDSA_PrivateKey& ecdsa) :
28 base_point(ecdsa.domain().get_base_point()),
29 order(ecdsa.domain().get_order()),
30 x(ecdsa.private_value()),
31 mod_order(order)
32 {
33 }
34
35 SecureVector<byte>
36 ECDSA_Signature_Operation::sign(const byte msg[], size_t msg_len,
37 RandomNumberGenerator& rng)
38 {
39 rng.add_entropy(msg, msg_len);
40
41 BigInt m(msg, msg_len);
42
43 BigInt r = 0, s = 0;
44
45 while(r == 0 || s == 0)
46 {
47 // This contortion is necessary for the tests
48 BigInt k;
49 k.randomize(rng, order.bits());
50
51 while(k >= order)
52 k.randomize(rng, order.bits() - 1);
53
54 PointGFp k_times_P = base_point * k;
55 r = mod_order.reduce(k_times_P.get_affine_x());
56 s = mod_order.multiply(inverse_mod(k, order), mul_add(x, r, m));
57 }
58
59 SecureVector<byte> output(2*order.bytes());
60 r.binary_encode(&output[output.size() / 2 - r.bytes()]);
61 s.binary_encode(&output[output.size() - s.bytes()]);
62 return output;
63 }
64
65 ECDSA_Verification_Operation::ECDSA_Verification_Operation(const ECDSA_PublicKey& ecdsa) :
66 base_point(ecdsa.domain().get_base_point()),
67 public_point(ecdsa.public_point()),
68 order(ecdsa.domain().get_order())
69 {
70 }
71
72 bool ECDSA_Verification_Operation::verify(const byte msg[], size_t msg_len,
73 const byte sig[], size_t sig_len)
74 {
75 if(sig_len != order.bytes()*2)
76 return false;
77
78 BigInt e(msg, msg_len);
79
80 BigInt r(sig, sig_len / 2);
81 BigInt s(sig + sig_len / 2, sig_len / 2);
82
83 if(r <= 0 || r >= order || s <= 0 || s >= order)
84 return false;
85
86 BigInt w = inverse_mod(s, order);
87
88 PointGFp R = w * multi_exponentiate(base_point, e,
89 public_point, r);
90
91 if(R.is_zero())
92 return false;
93
94 return (R.get_affine_x() % order == r);
95 }
96
97 }
Botan::EC_PrivateKey::private_value
const BigInt & private_value() const
Definition: ecc_key.cpp:70
Botan::KeyPair::signature_consistency_check
bool signature_consistency_check(RandomNumberGenerator &rng, const Private_Key &key, const std::string &padding)
Definition: keypair.cpp:47
Botan::BigInt
Definition: bigint.h:22
Botan::ECDSA_Verification_Operation::verify
bool verify(const byte msg[], size_t msg_len, const byte sig[], size_t sig_len)
Definition: ecdsa.cpp:72
Botan::RandomNumberGenerator::add_entropy
virtual void add_entropy(const byte in[], size_t length)=0
Botan::PointGFp
Definition: point_gfp.h:41
Botan::RandomNumberGenerator
Definition: rng.h:20
Botan::BigInt::bits
size_t bits() const
Definition: bigint.cpp:253
Botan::EC_PublicKey::public_point
const PointGFp & public_point() const
Definition: ecc_key.h:45
Botan::ECDSA_Signature_Operation::sign
SecureVector< byte > sign(const byte msg[], size_t msg_len, RandomNumberGenerator &rng)
Definition: ecdsa.cpp:36
Botan::PointGFp::get_affine_x
BigInt get_affine_x() const
Definition: point_gfp.cpp:400
Botan::byte
unsigned char byte
Definition: types.h:22
Botan::BigInt::randomize
void randomize(RandomNumberGenerator &rng, size_t bitsize=0)
Definition: big_rand.cpp:29
Botan::EC_PublicKey::domain
const EC_Group & domain() const
Definition: ecc_key.h:60
Botan::ECDSA_PublicKey
Definition: ecdsa.h:22
Botan::BigInt::binary_encode
void binary_encode(byte buf[]) const
Definition: bigint.cpp:340
Botan
Definition: algo_base.h:14
Botan::BigInt::bytes
size_t bytes() const
Definition: bigint.cpp:245
Botan::inverse_mod
BigInt inverse_mod(const BigInt &n, const BigInt &mod)
Definition: numthry.cpp:314
Botan::ECDSA_Signature_Operation::ECDSA_Signature_Operation
ECDSA_Signature_Operation(const ECDSA_PrivateKey &ecdsa)
Definition: ecdsa.cpp:27
Botan::Modular_Reducer::reduce
BigInt reduce(const BigInt &x) const
Definition: reducer.cpp:32
Botan::ECDSA_PrivateKey::check_key
bool check_key(RandomNumberGenerator &rng, bool) const
Definition: ecdsa.cpp:15
Botan::ECDSA_Verification_Operation::ECDSA_Verification_Operation
ECDSA_Verification_Operation(const ECDSA_PublicKey &ecdsa)
Definition: ecdsa.cpp:65
Botan::PointGFp::is_zero
bool is_zero() const
Definition: point_gfp.h:146
Botan::ECDSA_PrivateKey
Definition: ecdsa.h:64
Botan::SecureVector< byte >
Botan::Modular_Reducer::multiply
BigInt multiply(const BigInt &x, const BigInt &y) const
Definition: reducer.h:31
Botan::multi_exponentiate
PointGFp multi_exponentiate(const PointGFp &p1, const BigInt &z1, const PointGFp &p2, const BigInt &z2)
Definition: point_gfp.cpp:265
Botan::mul_add
BigInt mul_add(const BigInt &a, const BigInt &b, const BigInt &c)
Definition: mp_numth.cpp:33