aboutsummaryrefslogtreecommitdiffstats
path: root/crypto/secp256k1/ext.h
blob: b0f30b73c62667a8afa14699dfcb663ee9d36465 (plain) (blame)
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
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// secp256k1_context_create_sign_verify creates a context for signing and signature verification.
static secp256k1_context* secp256k1_context_create_sign_verify() {
    return secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
}

// secp256k1_ecdsa_recover_pubkey recovers the public key of an encoded compact signature.
//
// Returns: 1: recovery was successful
//          0: recovery was not successful
// Args:    ctx:        pointer to a context object (cannot be NULL)
//  Out:    pubkey_out: the serialized 65-byte public key of the signer (cannot be NULL)
//  In:     sigdata:    pointer to a 65-byte signature with the recovery id at the end (cannot be NULL)
//          msgdata:    pointer to a 32-byte message (cannot be NULL)
static int secp256k1_ecdsa_recover_pubkey(
    const secp256k1_context* ctx,
    unsigned char *pubkey_out,
    const unsigned char *sigdata,
    const unsigned char *msgdata
) {
    secp256k1_ecdsa_recoverable_signature sig;
    secp256k1_pubkey pubkey;

    if (!secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, &sig, sigdata, (int)sigdata[64])) {
        return 0;
    }
    if (!secp256k1_ecdsa_recover(ctx, &pubkey, &sig, msgdata)) {
        return 0;
    }
    size_t outputlen = 65;
    return secp256k1_ec_pubkey_serialize(ctx, pubkey_out, &outputlen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
}

// secp256k1_ecdsa_verify_enc verifies an encoded compact signature.
//
// Returns: 1: signature is valid
//          0: signature is invalid
// Args:    ctx:        pointer to a context object (cannot be NULL)
//  In:     sigdata:    pointer to a 64-byte signature (cannot be NULL)
//          msgdata:    pointer to a 32-byte message (cannot be NULL)
//          pubkeydata: pointer to public key data (cannot be NULL)
//          pubkeylen:  length of pubkeydata
static int secp256k1_ecdsa_verify_enc(
    const secp256k1_context* ctx,
    const unsigned char *sigdata,
    const unsigned char *msgdata,
    const unsigned char *pubkeydata,
    size_t pubkeylen
) {
    secp256k1_ecdsa_signature sig;
    secp256k1_pubkey pubkey;

    if (!secp256k1_ecdsa_signature_parse_compact(ctx, &sig, sigdata)) {
        return 0;
    }
    if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, pubkeylen)) {
        return 0;
    }
    return secp256k1_ecdsa_verify(ctx, &sig, msgdata, &pubkey);
}

// secp256k1_decompress_pubkey decompresses a public key.
//
// Returns: 1: public key is valid
//          0: public key is invalid
// Args:    ctx:        pointer to a context object (cannot be NULL)
//  Out:    pubkey_out: the serialized 65-byte public key (cannot be NULL)
//  In:     pubkeydata: pointer to 33 bytes of compressed public key data (cannot be NULL)
static int secp256k1_decompress_pubkey(
    const secp256k1_context* ctx,
    unsigned char *pubkey_out,
    const unsigned char *pubkeydata
) {
    secp256k1_pubkey pubkey;

    if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, 33)) {
        return 0;
    }
    size_t outputlen = 65;
    return secp256k1_ec_pubkey_serialize(ctx, pubkey_out, &outputlen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
}

// secp256k1_pubkey_scalar_mul multiplies a point by a scalar in constant time.
//
// Returns: 1: multiplication was successful
//          0: scalar was invalid (zero or overflow)
// Args:    ctx:      pointer to a context object (cannot be NULL)
//  Out:    point:    the multiplied point (usually secret)
//  In:     point:    pointer to a 64-byte public point,
//                    encoded as two 256bit big-endian numbers.
//          scalar:   a 32-byte scalar with which to multiply the point
int secp256k1_pubkey_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) {
    int ret = 0;
    int overflow = 0;
    secp256k1_fe feX, feY;
    secp256k1_gej res;
    secp256k1_ge ge;
    secp256k1_scalar s;
    ARG_CHECK(point != NULL);
    ARG_CHECK(scalar != NULL);
    (void)ctx;

    secp256k1_fe_set_b32(&feX, point);
    secp256k1_fe_set_b32(&feY, point+32);
    secp256k1_ge_set_xy(&ge, &feX, &feY);
    secp256k1_scalar_set_b32(&s, scalar, &overflow);
    if (overflow || secp256k1_scalar_is_zero(&s)) {
        ret = 0;
    } else {
        secp256k1_ecmult_const(&res, &ge, &s);
        secp256k1_ge_set_gej(&ge, &res);
        /* Note: can't use secp256k1_pubkey_save here because it is not constant time. */
        secp256k1_fe_normalize(&ge.x);
        secp256k1_fe_normalize(&ge.y);
        secp256k1_fe_get_b32(point, &ge.x);
        secp256k1_fe_get_b32(point+32, &ge.y);
        ret = 1;
    }
    secp256k1_scalar_clear(&s);
    return ret;
}