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
|
/*
* ECC Domain Parameters
*
* (C) 2007 Falko Strenzke, FlexSecure GmbH
* 2008 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ec_group.h>
#include <botan/ber_dec.h>
#include <botan/der_enc.h>
#include <botan/oids.h>
#include <botan/pem.h>
#include <botan/reducer.h>
namespace Botan {
EC_Group::EC_Group(const OID& domain_oid)
{
const std::string pem = PEM_for_named_group(OIDS::lookup(domain_oid));
if(pem == "")
{
throw Lookup_Error("No ECC domain data for '" + domain_oid.as_string() + "'");
}
*this = EC_Group(pem);
m_oid = domain_oid.as_string();
}
EC_Group::EC_Group(const std::string& str)
{
if(str == "")
return; // no initialization / uninitialized
try
{
std::vector<uint8_t> ber =
unlock(PEM_Code::decode_check_label(str, "EC PARAMETERS"));
*this = EC_Group(ber);
}
catch(Decoding_Error) // hmm, not PEM?
{
*this = EC_Group(OIDS::lookup(str));
}
}
EC_Group::EC_Group(const std::vector<uint8_t>& ber_data)
{
BER_Decoder ber(ber_data);
BER_Object obj = ber.get_next_object();
if(obj.type_tag == NULL_TAG)
throw Decoding_Error("Cannot handle ImplicitCA ECDSA parameters");
else if(obj.type_tag == OBJECT_ID)
{
OID dom_par_oid;
BER_Decoder(ber_data).decode(dom_par_oid);
*this = EC_Group(dom_par_oid);
}
else if(obj.type_tag == SEQUENCE)
{
BigInt p, a, b;
std::vector<uint8_t> sv_base_point;
BER_Decoder(ber_data)
.start_cons(SEQUENCE)
.decode_and_check<size_t>(1, "Unknown ECC param version code")
.start_cons(SEQUENCE)
.decode_and_check(OID("1.2.840.10045.1.1"),
"Only prime ECC fields supported")
.decode(p)
.end_cons()
.start_cons(SEQUENCE)
.decode_octet_string_bigint(a)
.decode_octet_string_bigint(b)
.end_cons()
.decode(sv_base_point, OCTET_STRING)
.decode(m_order)
.decode(m_cofactor)
.end_cons()
.verify_end();
m_curve = CurveGFp(p, a, b);
m_base_point = OS2ECP(sv_base_point, m_curve);
}
else
throw Decoding_Error("Unexpected tag while decoding ECC domain params");
}
std::vector<uint8_t>
EC_Group::DER_encode(EC_Group_Encoding form) const
{
if(form == EC_DOMPAR_ENC_EXPLICIT)
{
const size_t ecpVers1 = 1;
OID curve_type("1.2.840.10045.1.1");
const size_t p_bytes = m_curve.get_p().bytes();
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(ecpVers1)
.start_cons(SEQUENCE)
.encode(curve_type)
.encode(m_curve.get_p())
.end_cons()
.start_cons(SEQUENCE)
.encode(BigInt::encode_1363(m_curve.get_a(), p_bytes),
OCTET_STRING)
.encode(BigInt::encode_1363(m_curve.get_b(), p_bytes),
OCTET_STRING)
.end_cons()
.encode(EC2OSP(m_base_point, PointGFp::UNCOMPRESSED), OCTET_STRING)
.encode(m_order)
.encode(m_cofactor)
.end_cons()
.get_contents_unlocked();
}
else if(form == EC_DOMPAR_ENC_OID)
{
if(get_oid().empty())
{
throw Encoding_Error("Cannot encode EC_Group as OID because OID not set");
}
return DER_Encoder().encode(OID(get_oid())).get_contents_unlocked();
}
else if(form == EC_DOMPAR_ENC_IMPLICITCA)
return DER_Encoder().encode_null().get_contents_unlocked();
else
throw Internal_Error("EC_Group::DER_encode: Unknown encoding");
}
std::string EC_Group::PEM_encode() const
{
const std::vector<uint8_t> der = DER_encode(EC_DOMPAR_ENC_EXPLICIT);
return PEM_Code::encode(der, "EC PARAMETERS");
}
bool EC_Group::verify_group(RandomNumberGenerator& rng,
bool) const
{
//compute the discriminant
Modular_Reducer p(m_curve.get_p());
BigInt discriminant = p.multiply(4, m_curve.get_a());
discriminant += p.multiply(27, m_curve.get_b());
discriminant = p.reduce(discriminant);
//check the discriminant
if(discriminant == 0)
{
return false;
}
//check for valid cofactor
if(m_cofactor < 1)
{
return false;
}
//check if the base point is on the curve
if(!m_base_point.on_the_curve())
{
return false;
}
if((m_base_point * m_cofactor).is_zero())
{
return false;
}
//check if order is prime
if(!is_prime(m_order, rng, 128))
{
return false;
}
//check if order of the base point is correct
if(!(m_base_point * m_order).is_zero())
{
return false;
}
return true;
}
}
|
