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5075521e GT |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
0396401d | 5 | ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0, |
580b557b DSH |
6 | ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG, ECDSA_size, |
7 | ECDSA_sign, ECDSA_do_sign, ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, | |
8 | ECDSA_sign_ex, ECDSA_do_sign_ex - low level elliptic curve digital signature | |
bb9ad09e | 9 | algorithm (ECDSA) functions |
5075521e GT |
10 | |
11 | =head1 SYNOPSIS | |
12 | ||
13 | #include <openssl/ecdsa.h> | |
14 | ||
580b557b DSH |
15 | ECDSA_SIG *ECDSA_SIG_new(void); |
16 | void ECDSA_SIG_free(ECDSA_SIG *sig); | |
9267c11b | 17 | void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps); |
0396401d DMSP |
18 | const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig); |
19 | const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig); | |
7ca3ea22 | 20 | int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s); |
580b557b DSH |
21 | int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp); |
22 | ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len); | |
23 | int ECDSA_size(const EC_KEY *eckey); | |
24 | ||
25 | int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen, | |
26 | unsigned char *sig, unsigned int *siglen, EC_KEY *eckey); | |
27 | ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len, | |
28 | EC_KEY *eckey); | |
29 | ||
30 | int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen, | |
31 | const unsigned char *sig, int siglen, EC_KEY *eckey); | |
32 | int ECDSA_do_verify(const unsigned char *dgst, int dgst_len, | |
33 | const ECDSA_SIG *sig, EC_KEY* eckey); | |
34 | ||
35 | ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, | |
36 | const BIGNUM *kinv, const BIGNUM *rp, | |
37 | EC_KEY *eckey); | |
38 | int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp); | |
39 | int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen, | |
40 | unsigned char *sig, unsigned int *siglen, | |
41 | const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); | |
5075521e | 42 | |
5075521e GT |
43 | =head1 DESCRIPTION |
44 | ||
580b557b DSH |
45 | Note: these functions provide a low level interface to ECDSA. Most |
46 | applications should use the higher level B<EVP> interface such as | |
47 | L<EVP_DigestSignInit(3)> or L<EVP_DigestVerifyInit(3)> instead. | |
5075521e | 48 | |
580b557b DSH |
49 | B<ECDSA_SIG> is an opaque structure consisting of two BIGNUMs for the |
50 | B<r> and B<s> value of an ECDSA signature (see X9.62 or FIPS 186-2). | |
5075521e | 51 | |
721f3980 DSH |
52 | ECDSA_SIG_new() allocates an empty B<ECDSA_SIG> structure. Note: before |
53 | OpenSSL 1.1.0 the: the B<r> and B<s> components were initialised. | |
5075521e GT |
54 | |
55 | ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>. | |
56 | ||
580b557b | 57 | ECDSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained |
0396401d DMSP |
58 | in B<sig> and stores them in B<*pr> and B<*ps>, respectively. |
59 | The pointer B<pr> or B<ps> can be NULL, in which case the corresponding value | |
60 | is not returned. | |
61 | ||
62 | The values B<r>, B<s> can also be retrieved separately by the corresponding | |
63 | function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively. | |
5075521e | 64 | |
6a571a18 TS |
65 | The B<r> and B<s> values can be set by calling ECDSA_SIG_set0() and passing the |
66 | new values for B<r> and B<s> as parameters to the function. Calling this | |
67 | function transfers the memory management of the values to the ECDSA_SIG object, | |
68 | and therefore the values that have been passed in should not be freed directly | |
69 | after this function has been called. | |
70 | ||
580b557b DSH |
71 | i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature B<sig> and |
72 | writes the encoded signature to B<*pp> (note: if B<pp> is NULL i2d_ECDSA_SIG() | |
73 | returns the expected length in bytes of the DER encoded signature). | |
74 | i2d_ECDSA_SIG() returns the length of the DER encoded signature (or 0 on | |
75 | error). | |
5075521e | 76 | |
580b557b DSH |
77 | d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the decoded |
78 | signature in a newly allocated B<ECDSA_SIG> structure. B<*sig> points to the | |
79 | buffer containing the DER encoded signature of size B<len>. | |
5075521e | 80 | |
580b557b DSH |
81 | ECDSA_size() returns the maximum length of a DER encoded ECDSA signature |
82 | created with the private EC key B<eckey>. | |
5075521e | 83 | |
580b557b DSH |
84 | ECDSA_sign() computes a digital signature of the B<dgstlen> bytes hash value |
85 | B<dgst> using the private EC key B<eckey>. The DER encoded signatures is | |
424baabd | 86 | stored in B<sig> and its length is returned in B<sig_len>. Note: B<sig> must |
580b557b DSH |
87 | point to ECDSA_size(eckey) bytes of memory. The parameter B<type> is currently |
88 | ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with B<kinv> | |
b67d9889 NL |
89 | and B<rp> set to NULL. |
90 | ||
580b557b DSH |
91 | ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned |
92 | as a newly allocated B<ECDSA_SIG> structure (or NULL on error). ECDSA_do_sign() | |
93 | is a wrapper function for ECDSA_do_sign_ex() with B<kinv> and B<rp> set to | |
94 | NULL. | |
5075521e | 95 | |
580b557b DSH |
96 | ECDSA_verify() verifies that the signature in B<sig> of size B<siglen> is a |
97 | valid ECDSA signature of the hash value B<dgst> of size B<dgstlen> using the | |
98 | public key B<eckey>. The parameter B<type> is ignored. | |
5075521e | 99 | |
580b557b DSH |
100 | ECDSA_do_verify() is similar to ECDSA_verify() except the signature is |
101 | presented in the form of a pointer to an B<ECDSA_SIG> structure. | |
102 | ||
103 | The remaining functions utilise the internal B<kinv> and B<r> values used | |
104 | during signature computation. Most applications will never need to call these | |
105 | and some external ECDSA ENGINE implementations may not support them at all if | |
106 | either B<kinv> or B<r> is not B<NULL>. | |
b67d9889 | 107 | |
580b557b DSH |
108 | ECDSA_sign_setup() may be used to precompute parts of the signing operation. |
109 | B<eckey> is the private EC key and B<ctx> is a pointer to B<BN_CTX> structure | |
110 | (or NULL). The precomputed values or returned in B<kinv> and B<rp> and can be | |
111 | used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex(). | |
5075521e | 112 | |
580b557b DSH |
113 | ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes hash value |
114 | B<dgst> using the private EC key B<eckey> and the optional pre-computed values | |
424baabd | 115 | B<kinv> and B<rp>. The DER encoded signature is stored in B<sig> and its |
580b557b DSH |
116 | length is returned in B<sig_len>. Note: B<sig> must point to ECDSA_size(eckey) |
117 | bytes of memory. The parameter B<type> is ignored. | |
118 | ||
119 | ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is | |
120 | returned as a newly allocated B<ECDSA_SIG> structure (or NULL on error). | |
5075521e GT |
121 | |
122 | =head1 RETURN VALUES | |
123 | ||
6da34cfb KG |
124 | ECDSA_SIG_new() returns NULL if the allocation fails. |
125 | ||
6a571a18 TS |
126 | ECDSA_SIG_set0() returns 1 on success or 0 on failure. |
127 | ||
0396401d DMSP |
128 | ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, |
129 | or NULL if it is unset. | |
130 | ||
5075521e GT |
131 | ECDSA_size() returns the maximum length signature or 0 on error. |
132 | ||
580b557b DSH |
133 | ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful |
134 | or 0 on error. | |
135 | ||
136 | ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated | |
137 | B<ECDSA_SIG> structure or NULL on error. | |
5075521e GT |
138 | |
139 | ECDSA_verify() and ECDSA_do_verify() return 1 for a valid | |
140 | signature, 0 for an invalid signature and -1 on error. | |
9b86974e | 141 | The error codes can be obtained by L<ERR_get_error(3)>. |
5075521e GT |
142 | |
143 | =head1 EXAMPLES | |
144 | ||
580b557b DSH |
145 | Creating an ECDSA signature of a given SHA-256 hash value using the |
146 | named curve prime256v1 (aka P-256). | |
5075521e | 147 | |
b9b6a7e5 | 148 | First step: create an EC_KEY object (note: this part is B<not> ECDSA |
5075521e GT |
149 | specific) |
150 | ||
2947af32 | 151 | int ret; |
5075521e | 152 | ECDSA_SIG *sig; |
2947af32 | 153 | EC_KEY *eckey; |
e9b77246 | 154 | |
580b557b | 155 | eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1); |
2947af32 BB |
156 | if (eckey == NULL) |
157 | /* error */ | |
158 | if (EC_KEY_generate_key(eckey) == 0) | |
159 | /* error */ | |
580b557b DSH |
160 | |
161 | Second step: compute the ECDSA signature of a SHA-256 hash value | |
162 | using ECDSA_do_sign(): | |
163 | ||
164 | sig = ECDSA_do_sign(digest, 32, eckey); | |
2947af32 BB |
165 | if (sig == NULL) |
166 | /* error */ | |
580b557b DSH |
167 | |
168 | or using ECDSA_sign(): | |
5075521e GT |
169 | |
170 | unsigned char *buffer, *pp; | |
2947af32 | 171 | int buf_len; |
e9b77246 | 172 | |
5075521e | 173 | buf_len = ECDSA_size(eckey); |
2947af32 | 174 | buffer = OPENSSL_malloc(buf_len); |
5075521e | 175 | pp = buffer; |
2947af32 BB |
176 | if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0) |
177 | /* error */ | |
5075521e | 178 | |
580b557b | 179 | Third step: verify the created ECDSA signature using ECDSA_do_verify(): |
5075521e | 180 | |
580b557b | 181 | ret = ECDSA_do_verify(digest, 32, sig, eckey); |
5075521e | 182 | |
580b557b | 183 | or using ECDSA_verify(): |
5075521e | 184 | |
580b557b | 185 | ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); |
5075521e GT |
186 | |
187 | and finally evaluate the return value: | |
188 | ||
2947af32 BB |
189 | if (ret == 1) |
190 | /* signature ok */ | |
191 | else if (ret == 0) | |
192 | /* incorrect signature */ | |
193 | else | |
194 | /* error */ | |
5075521e GT |
195 | |
196 | =head1 CONFORMING TO | |
197 | ||
198 | ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 | |
199 | (Digital Signature Standard, DSS) | |
200 | ||
201 | =head1 SEE ALSO | |
202 | ||
87930507 | 203 | L<EC_KEY_new(3)>, |
580b557b DSH |
204 | L<EVP_DigestSignInit(3)>, |
205 | L<EVP_DigestVerifyInit(3)> | |
5075521e | 206 | |
e2f92610 RS |
207 | =head1 COPYRIGHT |
208 | ||
83cf7abf | 209 | Copyright 2004-2018 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 210 | |
4746f25a | 211 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
212 | this file except in compliance with the License. You can obtain a copy |
213 | in the file LICENSE in the source distribution or at | |
214 | L<https://www.openssl.org/source/license.html>. | |
215 | ||
216 | =cut |