1ecdsa(3) OpenSSL ecdsa(3)
2
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
12 #include <openssl/ecdsa.h>
13 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 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 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 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
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 struct
58 {
59 BIGNUM *r;
60 BIGNUM *s;
61 } ECDSA_SIG;
62 ECDSA_SIG_new() allocates a new ECDSA_SIG structure (note: this
64 function also allocates the BIGNUMs) and initialize it.
65 ECDSA_SIG_free() frees the ECDSA_SIG structure sig.
67 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 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 ECDSA_size() returns the maximum length of a DER encoded ECDSA
79 signature created with the private EC key eckey.
80 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 ECDSA_sign() is wrapper function for ECDSA_sign_ex with kinv and rp set
87 to NULL.
88 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 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 ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with kinv and
100 rp set to NULL.
101 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 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
112 ECDSA_size() returns the maximum length signature or 0 on error.
113 ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0 on
115 error.
116 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
122 Creating a ECDSA signature of given SHA-1 hash value using the named
123 curve secp192k1.
124 First step: create a EC_KEY object (note: this part is not ECDSA
126 specific)
127 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 Second step: compute the ECDSA signature of a SHA-1 hash value using
142 ECDSA_do_sign
143 sig = ECDSA_do_sign(digest, 20, eckey);
145 if (sig == NULL)
146 {
147 /* error */
148 }
149 or using ECDSA_sign
151 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 Third step: verify the created ECDSA signature using ECDSA_do_verify
163 ret = ECDSA_do_verify(digest, 20, sig, eckey);
165 or using ECDSA_verify
167 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
169 and finally evaluate the return value:
171 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
186 ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
187 (Digital Signature Standard, DSS)
188
190 dsa(3), rsa(3)
191
193 The ecdsa implementation was first introduced in OpenSSL 0.9.8
194
196 Nils Larsch for the OpenSSL project (http://www.openssl.org).
1971.0.2o 2020-01-28 ecdsa(3)