ECDSA_SIG_free(3ssl)

1ecdsa(3)                            OpenSSL                           ecdsa(3)
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NAME

6       ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG,
7       ECDSA_size, ECDSA_sign_setup, ECDSA_sign, ECDSA_sign_ex, ECDSA_verify,
8       ECDSA_do_sign, ECDSA_do_sign_ex, ECDSA_do_verify - Elliptic Curve
9       Digital Signature Algorithm
10

SYNOPSIS

12        #include <openssl/ecdsa.h>
13
14        ECDSA_SIG*     ECDSA_SIG_new(void);
15        void           ECDSA_SIG_free(ECDSA_SIG *sig);
16        int            i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
17        ECDSA_SIG*     d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
18                       long len);
19
20        ECDSA_SIG*     ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
21                               EC_KEY *eckey);
22        ECDSA_SIG*     ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
23                               const BIGNUM *kinv, const BIGNUM *rp,
24                               EC_KEY *eckey);
25        int            ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
26                               const ECDSA_SIG *sig, EC_KEY* eckey);
27        int            ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
28                               BIGNUM **kinv, BIGNUM **rp);
29        int            ECDSA_sign(int type, const unsigned char *dgst,
30                               int dgstlen, unsigned char *sig,
31                               unsigned int *siglen, EC_KEY *eckey);
32        int            ECDSA_sign_ex(int type, const unsigned char *dgst,
33                               int dgstlen, unsigned char *sig,
34                               unsigned int *siglen, const BIGNUM *kinv,
35                               const BIGNUM *rp, EC_KEY *eckey);
36        int            ECDSA_verify(int type, const unsigned char *dgst,
37                               int dgstlen, const unsigned char *sig,
38                               int siglen, EC_KEY *eckey);
39        int            ECDSA_size(const EC_KEY *eckey);
40
41        const ECDSA_METHOD*    ECDSA_OpenSSL(void);
42        void           ECDSA_set_default_method(const ECDSA_METHOD *meth);
43        const ECDSA_METHOD*    ECDSA_get_default_method(void);
44        int            ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
45
46        int            ECDSA_get_ex_new_index(long argl, void *argp,
47                               CRYPTO_EX_new *new_func,
48                               CRYPTO_EX_dup *dup_func,
49                               CRYPTO_EX_free *free_func);
50        int            ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
51        void*          ECDSA_get_ex_data(EC_KEY *d, int idx);
52

DESCRIPTION

54       The ECDSA_SIG structure consists of two BIGNUMs for the r and s value
55       of a ECDSA signature (see X9.62 or FIPS 186-2).
56
57        struct
58               {
59               BIGNUM *r;
60               BIGNUM *s;
61        } ECDSA_SIG;
62
63       ECDSA_SIG_new() allocates a new ECDSA_SIG structure (note: this
64       function also allocates the BIGNUMs) and initialize it.
65
66       ECDSA_SIG_free() frees the ECDSA_SIG structure sig.
67
68       i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature sig and
69       writes the encoded signature to *pp (note: if pp is NULL i2d_ECDSA_SIG
70       returns the expected length in bytes of the DER encoded signature).
71       i2d_ECDSA_SIG returns the length of the DER encoded signature (or 0 on
72       error).
73
74       d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the
75       decoded signature in a newly allocated ECDSA_SIG structure.  *sig
76       points to the buffer containing the DER encoded signature of size len.
77
78       ECDSA_size() returns the maximum length of a DER encoded ECDSA
79       signature created with the private EC key eckey.
80
81       ECDSA_sign_setup() may be used to precompute parts of the signing
82       operation. eckey is the private EC key and ctx is a pointer to BN_CTX
83       structure (or NULL). The precomputed values or returned in kinv and rp
84       and can be used in a later call to ECDSA_sign_ex or ECDSA_do_sign_ex.
85
86       ECDSA_sign() is wrapper function for ECDSA_sign_ex with kinv and rp set
87       to NULL.
88
89       ECDSA_sign_ex() computes a digital signature of the dgstlen bytes hash
90       value dgst using the private EC key eckey and the optional pre-computed
91       values kinv and rp. The DER encoded signatures is stored in sig and
92       it's length is returned in sig_len. Note: sig must point to ECDSA_size
93       bytes of memory. The parameter type is ignored.
94
95       ECDSA_verify() verifies that the signature in sig of size siglen is a
96       valid ECDSA signature of the hash value dgst of size dgstlen using the
97       public key eckey.  The parameter type is ignored.
98
99       ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with kinv and
100       rp set to NULL.
101
102       ECDSA_do_sign_ex() computes a digital signature of the dgst_len bytes
103       hash value dgst using the private key eckey and the optional pre-
104       computed values kinv and rp. The signature is returned in a newly
105       allocated ECDSA_SIG structure (or NULL on error).
106
107       ECDSA_do_verify() verifies that the signature sig is a valid ECDSA
108       signature of the hash value dgst of size dgst_len using the public key
109       eckey.
110

RETURN VALUES

112       ECDSA_size() returns the maximum length signature or 0 on error.
113
114       ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0 on
115       error.
116
117       ECDSA_verify() and ECDSA_do_verify() return 1 for a valid signature, 0
118       for an invalid signature and -1 on error.  The error codes can be
119       obtained by ERR_get_error(3).
120

EXAMPLES

122       Creating a ECDSA signature of given SHA-1 hash value using the named
123       curve secp192k1.
124
125       First step: create a EC_KEY object (note: this part is not ECDSA
126       specific)
127
128        int        ret;
129        ECDSA_SIG *sig;
130        EC_KEY    *eckey;
131        eckey = EC_KEY_new_by_curve_name(NID_secp192k1);
132        if (eckey == NULL)
133               {
134               /* error */
135               }
136        if (!EC_KEY_generate_key(eckey))
137               {
138               /* error */
139               }
140
141       Second step: compute the ECDSA signature of a SHA-1 hash value using
142       ECDSA_do_sign
143
144        sig = ECDSA_do_sign(digest, 20, eckey);
145        if (sig == NULL)
146               {
147               /* error */
148               }
149
150       or using ECDSA_sign
151
152        unsigned char *buffer, *pp;
153        int            buf_len;
154        buf_len = ECDSA_size(eckey);
155        buffer  = OPENSSL_malloc(buf_len);
156        pp = buffer;
157        if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
158               {
159               /* error */
160               }
161
162       Third step: verify the created ECDSA signature using ECDSA_do_verify
163
164        ret = ECDSA_do_verify(digest, 20, sig, eckey);
165
166       or using ECDSA_verify
167
168        ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
169
170       and finally evaluate the return value:
171
172        if (ret == -1)
173               {
174               /* error */
175               }
176        else if (ret == 0)
177               {
178               /* incorrect signature */
179               }
180        else   /* ret == 1 */
181               {
182               /* signature ok */
183               }
184

CONFORMING TO

186       ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
187       (Digital Signature Standard, DSS)
188

HISTORY

193       The ecdsa implementation was first introduced in OpenSSL 0.9.8
194

AUTHOR

196       Nils Larsch for the OpenSSL project (http://www.openssl.org).
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2001.0.2o                            2020-01-28                          ecdsa(3)