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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, |
bbda7997 MC |
6 | ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_size, ECDSA_sign, ECDSA_do_sign, |
7 | ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex, | |
8 | ECDSA_do_sign_ex - low level elliptic curve digital signature algorithm (ECDSA) | |
9 | 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 ECDSA_size(const EC_KEY *eckey); |
22 | ||
23 | int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen, | |
24 | unsigned char *sig, unsigned int *siglen, EC_KEY *eckey); | |
25 | ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len, | |
26 | EC_KEY *eckey); | |
27 | ||
28 | int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen, | |
29 | const unsigned char *sig, int siglen, EC_KEY *eckey); | |
30 | int ECDSA_do_verify(const unsigned char *dgst, int dgst_len, | |
31 | const ECDSA_SIG *sig, EC_KEY* eckey); | |
32 | ||
33 | ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, | |
34 | const BIGNUM *kinv, const BIGNUM *rp, | |
35 | EC_KEY *eckey); | |
36 | int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp); | |
37 | int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen, | |
38 | unsigned char *sig, unsigned int *siglen, | |
39 | const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); | |
5075521e | 40 | |
5075521e GT |
41 | =head1 DESCRIPTION |
42 | ||
580b557b DSH |
43 | Note: these functions provide a low level interface to ECDSA. Most |
44 | applications should use the higher level B<EVP> interface such as | |
45 | L<EVP_DigestSignInit(3)> or L<EVP_DigestVerifyInit(3)> instead. | |
5075521e | 46 | |
580b557b DSH |
47 | B<ECDSA_SIG> is an opaque structure consisting of two BIGNUMs for the |
48 | B<r> and B<s> value of an ECDSA signature (see X9.62 or FIPS 186-2). | |
5075521e | 49 | |
721f3980 DSH |
50 | ECDSA_SIG_new() allocates an empty B<ECDSA_SIG> structure. Note: before |
51 | OpenSSL 1.1.0 the: the B<r> and B<s> components were initialised. | |
5075521e GT |
52 | |
53 | ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>. | |
54 | ||
580b557b | 55 | ECDSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained |
0396401d DMSP |
56 | in B<sig> and stores them in B<*pr> and B<*ps>, respectively. |
57 | The pointer B<pr> or B<ps> can be NULL, in which case the corresponding value | |
58 | is not returned. | |
59 | ||
60 | The values B<r>, B<s> can also be retrieved separately by the corresponding | |
61 | function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively. | |
5075521e | 62 | |
6a571a18 TS |
63 | The B<r> and B<s> values can be set by calling ECDSA_SIG_set0() and passing the |
64 | new values for B<r> and B<s> as parameters to the function. Calling this | |
65 | function transfers the memory management of the values to the ECDSA_SIG object, | |
66 | and therefore the values that have been passed in should not be freed directly | |
67 | after this function has been called. | |
68 | ||
bbda7997 MC |
69 | See L<i2d_ECDSA_SIG(3)> and L<d2i_ECDSA_SIG(3)> for information about encoding |
70 | and decoding ECDSA signatures to/from DER. | |
5075521e | 71 | |
580b557b DSH |
72 | ECDSA_size() returns the maximum length of a DER encoded ECDSA signature |
73 | created with the private EC key B<eckey>. | |
5075521e | 74 | |
580b557b DSH |
75 | ECDSA_sign() computes a digital signature of the B<dgstlen> bytes hash value |
76 | B<dgst> using the private EC key B<eckey>. The DER encoded signatures is | |
424baabd | 77 | stored in B<sig> and its length is returned in B<sig_len>. Note: B<sig> must |
580b557b DSH |
78 | point to ECDSA_size(eckey) bytes of memory. The parameter B<type> is currently |
79 | ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with B<kinv> | |
b67d9889 NL |
80 | and B<rp> set to NULL. |
81 | ||
580b557b DSH |
82 | ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned |
83 | as a newly allocated B<ECDSA_SIG> structure (or NULL on error). ECDSA_do_sign() | |
84 | is a wrapper function for ECDSA_do_sign_ex() with B<kinv> and B<rp> set to | |
85 | NULL. | |
5075521e | 86 | |
580b557b DSH |
87 | ECDSA_verify() verifies that the signature in B<sig> of size B<siglen> is a |
88 | valid ECDSA signature of the hash value B<dgst> of size B<dgstlen> using the | |
89 | public key B<eckey>. The parameter B<type> is ignored. | |
5075521e | 90 | |
580b557b DSH |
91 | ECDSA_do_verify() is similar to ECDSA_verify() except the signature is |
92 | presented in the form of a pointer to an B<ECDSA_SIG> structure. | |
93 | ||
94 | The remaining functions utilise the internal B<kinv> and B<r> values used | |
95 | during signature computation. Most applications will never need to call these | |
96 | and some external ECDSA ENGINE implementations may not support them at all if | |
97 | either B<kinv> or B<r> is not B<NULL>. | |
b67d9889 | 98 | |
580b557b DSH |
99 | ECDSA_sign_setup() may be used to precompute parts of the signing operation. |
100 | B<eckey> is the private EC key and B<ctx> is a pointer to B<BN_CTX> structure | |
101 | (or NULL). The precomputed values or returned in B<kinv> and B<rp> and can be | |
102 | used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex(). | |
5075521e | 103 | |
580b557b DSH |
104 | ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes hash value |
105 | B<dgst> using the private EC key B<eckey> and the optional pre-computed values | |
424baabd | 106 | B<kinv> and B<rp>. The DER encoded signature is stored in B<sig> and its |
580b557b DSH |
107 | length is returned in B<sig_len>. Note: B<sig> must point to ECDSA_size(eckey) |
108 | bytes of memory. The parameter B<type> is ignored. | |
109 | ||
110 | ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is | |
111 | returned as a newly allocated B<ECDSA_SIG> structure (or NULL on error). | |
5075521e GT |
112 | |
113 | =head1 RETURN VALUES | |
114 | ||
6da34cfb KG |
115 | ECDSA_SIG_new() returns NULL if the allocation fails. |
116 | ||
6a571a18 TS |
117 | ECDSA_SIG_set0() returns 1 on success or 0 on failure. |
118 | ||
0396401d DMSP |
119 | ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, |
120 | or NULL if it is unset. | |
121 | ||
5075521e GT |
122 | ECDSA_size() returns the maximum length signature or 0 on error. |
123 | ||
580b557b DSH |
124 | ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful |
125 | or 0 on error. | |
126 | ||
127 | ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated | |
128 | B<ECDSA_SIG> structure or NULL on error. | |
5075521e GT |
129 | |
130 | ECDSA_verify() and ECDSA_do_verify() return 1 for a valid | |
131 | signature, 0 for an invalid signature and -1 on error. | |
9b86974e | 132 | The error codes can be obtained by L<ERR_get_error(3)>. |
5075521e GT |
133 | |
134 | =head1 EXAMPLES | |
135 | ||
580b557b DSH |
136 | Creating an ECDSA signature of a given SHA-256 hash value using the |
137 | named curve prime256v1 (aka P-256). | |
5075521e | 138 | |
b9b6a7e5 | 139 | First step: create an EC_KEY object (note: this part is B<not> ECDSA |
5075521e GT |
140 | specific) |
141 | ||
2947af32 | 142 | int ret; |
5075521e | 143 | ECDSA_SIG *sig; |
2947af32 | 144 | EC_KEY *eckey; |
e9b77246 | 145 | |
580b557b | 146 | eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1); |
2947af32 BB |
147 | if (eckey == NULL) |
148 | /* error */ | |
149 | if (EC_KEY_generate_key(eckey) == 0) | |
150 | /* error */ | |
580b557b DSH |
151 | |
152 | Second step: compute the ECDSA signature of a SHA-256 hash value | |
153 | using ECDSA_do_sign(): | |
154 | ||
155 | sig = ECDSA_do_sign(digest, 32, eckey); | |
2947af32 BB |
156 | if (sig == NULL) |
157 | /* error */ | |
580b557b DSH |
158 | |
159 | or using ECDSA_sign(): | |
5075521e GT |
160 | |
161 | unsigned char *buffer, *pp; | |
2947af32 | 162 | int buf_len; |
e9b77246 | 163 | |
5075521e | 164 | buf_len = ECDSA_size(eckey); |
2947af32 | 165 | buffer = OPENSSL_malloc(buf_len); |
5075521e | 166 | pp = buffer; |
2947af32 BB |
167 | if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0) |
168 | /* error */ | |
5075521e | 169 | |
580b557b | 170 | Third step: verify the created ECDSA signature using ECDSA_do_verify(): |
5075521e | 171 | |
580b557b | 172 | ret = ECDSA_do_verify(digest, 32, sig, eckey); |
5075521e | 173 | |
580b557b | 174 | or using ECDSA_verify(): |
5075521e | 175 | |
580b557b | 176 | ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); |
5075521e GT |
177 | |
178 | and finally evaluate the return value: | |
179 | ||
2947af32 BB |
180 | if (ret == 1) |
181 | /* signature ok */ | |
182 | else if (ret == 0) | |
183 | /* incorrect signature */ | |
184 | else | |
185 | /* error */ | |
5075521e GT |
186 | |
187 | =head1 CONFORMING TO | |
188 | ||
189 | ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 | |
190 | (Digital Signature Standard, DSS) | |
191 | ||
192 | =head1 SEE ALSO | |
193 | ||
87930507 | 194 | L<EC_KEY_new(3)>, |
580b557b | 195 | L<EVP_DigestSignInit(3)>, |
bbda7997 MC |
196 | L<EVP_DigestVerifyInit(3)>, |
197 | L<i2d_ECDSA_SIG(3)>, | |
198 | L<d2i_ECDSA_SIG(3)> | |
5075521e | 199 | |
e2f92610 RS |
200 | =head1 COPYRIGHT |
201 | ||
83cf7abf | 202 | Copyright 2004-2018 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 203 | |
4746f25a | 204 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
205 | this file except in compliance with the License. You can obtain a copy |
206 | in the file LICENSE in the source distribution or at | |
207 | L<https://www.openssl.org/source/license.html>. | |
208 | ||
209 | =cut |