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
|
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
*
* All curves taken from NIST recommendation paper of July 1999
* Available at http://csrc.nist.gov/cryptval/dss.htm
*/
#include "tomcrypt.h"
/**
@file ecc_import.c
ECC Crypto, Tom St Denis
*/
#if defined(LTC_MECC) && defined(LTC_DER)
static int is_point(ecc_key *key)
{
void *prime, *b, *t1, *t2;
int err;
if ((err = mp_init_multi(&prime, &b, &t1, &t2, NULL)) != CRYPT_OK) {
return err;
}
/* load prime and b */
if ((err = mp_read_radix(prime, key->dp->prime, 16)) != CRYPT_OK) { goto error; }
if ((err = mp_read_radix(b, key->dp->B, 16)) != CRYPT_OK) { goto error; }
/* compute y^2 */
if ((err = mp_sqr(key->pubkey.y, t1)) != CRYPT_OK) { goto error; }
/* compute x^3 */
if ((err = mp_sqr(key->pubkey.x, t2)) != CRYPT_OK) { goto error; }
if ((err = mp_mod(t2, prime, t2)) != CRYPT_OK) { goto error; }
if ((err = mp_mul(key->pubkey.x, t2, t2)) != CRYPT_OK) { goto error; }
/* compute y^2 - x^3 */
if ((err = mp_sub(t1, t2, t1)) != CRYPT_OK) { goto error; }
/* compute y^2 - x^3 + 3x */
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_mod(t1, prime, t1)) != CRYPT_OK) { goto error; }
while (mp_cmp_d(t1, 0) == LTC_MP_LT) {
if ((err = mp_add(t1, prime, t1)) != CRYPT_OK) { goto error; }
}
while (mp_cmp(t1, prime) != LTC_MP_LT) {
if ((err = mp_sub(t1, prime, t1)) != CRYPT_OK) { goto error; }
}
/* compare to b */
if (mp_cmp(t1, b) != LTC_MP_EQ) {
err = CRYPT_INVALID_PACKET;
} else {
err = CRYPT_OK;
}
error:
mp_clear_multi(prime, b, t1, t2, NULL);
return err;
}
/**
Import an ECC key from a binary packet
@param in The packet to import
@param inlen The length of the packet
@param key [out] The destination of the import
@return CRYPT_OK if successful, upon error all allocated memory will be freed
*/
int ecc_import(const unsigned char *in, unsigned long inlen, ecc_key *key)
{
return ecc_import_ex(in, inlen, key, NULL);
}
/**
Import an ECC key from a binary packet, using user supplied domain params rather than one of the NIST ones
@param in The packet to import
@param inlen The length of the packet
@param key [out] The destination of the import
@param dp pointer to user supplied params; must be the same as the params used when exporting
@return CRYPT_OK if successful, upon error all allocated memory will be freed
*/
int ecc_import_ex(const unsigned char *in, unsigned long inlen, ecc_key *key, const ltc_ecc_set_type *dp)
{
unsigned long key_size;
unsigned char flags[1];
int err;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(ltc_mp.name != NULL);
/* init key */
if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, NULL) != CRYPT_OK) {
return CRYPT_MEM;
}
/* find out what type of key it is */
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, &flags,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
if (flags[0] == 1) {
/* private key */
key->type = PK_PRIVATE;
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, flags,
LTC_ASN1_SHORT_INTEGER, 1UL, &key_size,
LTC_ASN1_INTEGER, 1UL, key->pubkey.x,
LTC_ASN1_INTEGER, 1UL, key->pubkey.y,
LTC_ASN1_INTEGER, 1UL, key->k,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
} else {
/* public key */
key->type = PK_PUBLIC;
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, flags,
LTC_ASN1_SHORT_INTEGER, 1UL, &key_size,
LTC_ASN1_INTEGER, 1UL, key->pubkey.x,
LTC_ASN1_INTEGER, 1UL, key->pubkey.y,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
}
if (dp == NULL) {
/* find the idx */
for (key->idx = 0; ltc_ecc_sets[key->idx].size && (unsigned long)ltc_ecc_sets[key->idx].size != key_size; ++key->idx);
if (ltc_ecc_sets[key->idx].size == 0) {
err = CRYPT_INVALID_PACKET;
goto done;
}
key->dp = <c_ecc_sets[key->idx];
} else {
key->idx = -1;
key->dp = dp;
}
/* set z */
if ((err = mp_set(key->pubkey.z, 1)) != CRYPT_OK) { goto done; }
/* is it a point on the curve? */
if ((err = is_point(key)) != CRYPT_OK) {
goto done;
}
/* we're good */
return CRYPT_OK;
done:
mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL);
return err;
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */
|
