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

Botan 1.10.16

dsa.cpp
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1 /*
2 * DSA
3 * (C) 1999-2010 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7
8 #include <botan/dsa.h>
9 #include <botan/numthry.h>
10 #include <botan/keypair.h>
11
12 namespace Botan {
13
14 /*
15 * DSA_PublicKey Constructor
16 */
17 DSA_PublicKey::DSA_PublicKey(const DL_Group& grp, const BigInt& y1)
18 {
19 group = grp;
20 y = y1;
21 }
22
23 /*
24 * Create a DSA private key
25 */
26 DSA_PrivateKey::DSA_PrivateKey(RandomNumberGenerator& rng,
27 const DL_Group& grp,
28 const BigInt& x_arg)
29 {
30 group = grp;
31 x = x_arg;
32
33 if(x == 0)
34 x = BigInt::random_integer(rng, 2, group_q() - 1);
35
36 y = power_mod(group_g(), x, group_p());
37
38 if(x_arg == 0)
39 gen_check(rng);
40 else
41 load_check(rng);
42 }
43
44 DSA_PrivateKey::DSA_PrivateKey(const AlgorithmIdentifier& alg_id,
45 const MemoryRegion<byte>& key_bits,
46 RandomNumberGenerator& rng) :
47 DL_Scheme_PrivateKey(alg_id, key_bits, DL_Group::ANSI_X9_57)
48 {
49 y = power_mod(group_g(), x, group_p());
50
51 load_check(rng);
52 }
53
54 /*
55 * Check Private DSA Parameters
56 */
57 bool DSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
58 {
59 if(!DL_Scheme_PrivateKey::check_key(rng, strong) || x >= group_q())
60 return false;
61
62 if(!strong)
63 return true;
64
65 return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-1)");
66 }
67
68 DSA_Signature_Operation::DSA_Signature_Operation(const DSA_PrivateKey& dsa) :
69 q(dsa.group_q()),
70 x(dsa.get_x()),
71 powermod_g_p(dsa.group_g(), dsa.group_p()),
72 mod_q(dsa.group_q())
73 {
74 }
75
76 SecureVector<byte>
77 DSA_Signature_Operation::sign(const byte msg[], size_t msg_len,
78 RandomNumberGenerator& rng)
79 {
80 rng.add_entropy(msg, msg_len);
81
82 BigInt i(msg, msg_len);
83 BigInt r = 0, s = 0;
84
85 while(r == 0 || s == 0)
86 {
87 BigInt k;
88 do
89 k.randomize(rng, q.bits());
90 while(k >= q);
91
92 r = mod_q.reduce(powermod_g_p(k));
93 s = mod_q.multiply(inverse_mod(k, q), mul_add(x, r, i));
94 }
95
96 SecureVector<byte> output(2*q.bytes());
97 r.binary_encode(&output[output.size() / 2 - r.bytes()]);
98 s.binary_encode(&output[output.size() - s.bytes()]);
99 return output;
100 }
101
102 DSA_Verification_Operation::DSA_Verification_Operation(const DSA_PublicKey& dsa) :
103 q(dsa.group_q()), y(dsa.get_y())
104 {
105 powermod_g_p = Fixed_Base_Power_Mod(dsa.group_g(), dsa.group_p());
106 powermod_y_p = Fixed_Base_Power_Mod(y, dsa.group_p());
107 mod_p = Modular_Reducer(dsa.group_p());
108 mod_q = Modular_Reducer(dsa.group_q());
109 }
110
111 bool DSA_Verification_Operation::verify(const byte msg[], size_t msg_len,
112 const byte sig[], size_t sig_len)
113 {
114 const BigInt& q = mod_q.get_modulus();
115
116 if(sig_len != 2*q.bytes() || msg_len > q.bytes())
117 return false;
118
119 BigInt r(sig, q.bytes());
120 BigInt s(sig + q.bytes(), q.bytes());
121 BigInt i(msg, msg_len);
122
123 if(r <= 0 || r >= q || s <= 0 || s >= q)
124 return false;
125
126 s = inverse_mod(s, q);
127 s = mod_p.multiply(powermod_g_p(mod_q.multiply(s, i)),
128 powermod_y_p(mod_q.multiply(s, r)));
129
130 return (mod_q.reduce(s) == r);
131 }
132
133 }
Botan::DL_Scheme_PrivateKey
Definition: dl_algo.h:85
Botan::Public_Key::load_check
virtual void load_check(RandomNumberGenerator &rng) const
Definition: pk_keys.cpp:31
Botan::DSA_PrivateKey::check_key
bool check_key(RandomNumberGenerator &rng, bool strong) const
Definition: dsa.cpp:57
Botan::DSA_PublicKey::DSA_PublicKey
DSA_PublicKey()
Definition: dsa.h:39
Botan::Fixed_Base_Power_Mod
Definition: pow_mod.h:87
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::RandomNumberGenerator::add_entropy
virtual void add_entropy(const byte in[], size_t length)=0
Botan::RandomNumberGenerator
Definition: rng.h:20
Botan::BigInt::bits
size_t bits() const
Definition: bigint.cpp:253
Botan::DL_Scheme_PrivateKey::check_key
bool check_key(RandomNumberGenerator &rng, bool) const
Definition: dl_algo.cpp:67
Botan::BigInt::random_integer
static BigInt random_integer(RandomNumberGenerator &rng, const BigInt &min, const BigInt &max)
Definition: big_rand.cpp:50
Botan::byte
unsigned char byte
Definition: types.h:22
Botan::DL_Group
Definition: dl_group.h:20
Botan::DSA_Verification_Operation::DSA_Verification_Operation
DSA_Verification_Operation(const DSA_PublicKey &dsa)
Definition: dsa.cpp:102
Botan::DSA_Verification_Operation::verify
bool verify(const byte msg[], size_t msg_len, const byte sig[], size_t sig_len)
Definition: dsa.cpp:111
Botan::BigInt::randomize
void randomize(RandomNumberGenerator &rng, size_t bitsize=0)
Definition: big_rand.cpp:29
Botan::BigInt::binary_encode
void binary_encode(byte buf[]) const
Definition: bigint.cpp:340
Botan::DSA_PrivateKey
Definition: dsa.h:45
Botan::MemoryRegion< byte >
Botan
Definition: algo_base.h:14
Botan::BigInt::bytes
size_t bytes() const
Definition: bigint.cpp:245
Botan::Private_Key::load_check
void load_check(RandomNumberGenerator &rng) const
Definition: pk_keys.cpp:40
Botan::DSA_Signature_Operation::sign
SecureVector< byte > sign(const byte msg[], size_t msg_len, RandomNumberGenerator &rng)
Definition: dsa.cpp:77
Botan::DSA_PublicKey
Definition: dsa.h:21
Botan::DSA_Signature_Operation::DSA_Signature_Operation
DSA_Signature_Operation(const DSA_PrivateKey &dsa)
Definition: dsa.cpp:68
Botan::Modular_Reducer::get_modulus
const BigInt & get_modulus() const
Definition: reducer.h:21
Botan::inverse_mod
BigInt inverse_mod(const BigInt &n, const BigInt &mod)
Definition: numthry.cpp:314
Botan::DL_Scheme_PublicKey::group_p
const BigInt & group_p() const
Definition: dl_algo.h:44
Botan::Modular_Reducer::reduce
BigInt reduce(const BigInt &x) const
Definition: reducer.cpp:32
Botan::power_mod
BigInt power_mod(const BigInt &base, const BigInt &exp, const BigInt &mod)
Definition: numthry.cpp:366
Botan::DL_Scheme_PrivateKey::x
BigInt x
Definition: dl_algo.h:109
Botan::DL_Scheme_PublicKey::group
DL_Group group
Definition: dl_algo.h:79
Botan::AlgorithmIdentifier
Definition: alg_id.h:20
Botan::SecureVector< byte >
Botan::DL_Scheme_PrivateKey::get_x
const BigInt & get_x() const
Definition: dl_algo.h:95
Botan::DL_Scheme_PublicKey::group_g
const BigInt & group_g() const
Definition: dl_algo.h:56
Botan::DL_Scheme_PublicKey::group_q
const BigInt & group_q() const
Definition: dl_algo.h:50
Botan::Modular_Reducer
Definition: reducer.h:18
Botan::DSA_PrivateKey::DSA_PrivateKey
DSA_PrivateKey(const AlgorithmIdentifier &alg_id, const MemoryRegion< byte > &key_bits, RandomNumberGenerator &rng)
Definition: dsa.cpp:44
Botan::Modular_Reducer::multiply
BigInt multiply(const BigInt &x, const BigInt &y) const
Definition: reducer.h:31
Botan::mul_add
BigInt mul_add(const BigInt &a, const BigInt &b, const BigInt &c)
Definition: mp_numth.cpp:33
Botan::DL_Scheme_PublicKey::y
BigInt y
Definition: dl_algo.h:74