5 ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0,
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)
13 #include <openssl/ecdsa.h>
15 ECDSA_SIG *ECDSA_SIG_new(void);
16 void ECDSA_SIG_free(ECDSA_SIG *sig);
17 void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
18 const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
19 const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
20 int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);
22 The following functions have been deprecated since OpenSSL 3.0, and can be
23 hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
24 see L<openssl_user_macros(7)>:
26 int ECDSA_size(const EC_KEY *eckey);
28 int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen,
29 unsigned char *sig, unsigned int *siglen, EC_KEY *eckey);
30 ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
33 int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen,
34 const unsigned char *sig, int siglen, EC_KEY *eckey);
35 int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
36 const ECDSA_SIG *sig, EC_KEY* eckey);
38 ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
39 const BIGNUM *kinv, const BIGNUM *rp,
41 int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp);
42 int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen,
43 unsigned char *sig, unsigned int *siglen,
44 const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey);
48 B<ECDSA_SIG> is an opaque structure consisting of two BIGNUMs for the
49 I<r> and I<s> value of an ECDSA signature (see X9.62 or FIPS186-2).
51 ECDSA_SIG_new() allocates an empty B<ECDSA_SIG> structure. Note: before
52 OpenSSL 1.1.0 the: the I<r> and I<s> components were initialised.
54 ECDSA_SIG_free() frees the B<ECDSA_SIG> structure I<sig>.
56 ECDSA_SIG_get0() returns internal pointers the I<r> and I<s> values contained
57 in I<sig> and stores them in I<*pr> and I<*ps>, respectively.
58 The pointer I<pr> or I<ps> can be NULL, in which case the corresponding value
61 The values I<r>, I<s> can also be retrieved separately by the corresponding
62 function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively.
64 Non-NULL I<r> and I<s> values can be set on the I<sig> by calling
65 ECDSA_SIG_set0(). Calling this function transfers the memory management of the
66 values to the B<ECDSA_SIG> object, and therefore the values that have been
67 passed in should not be freed by the caller.
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.
72 All of the functions described below are deprecated. Applications should
73 use the higher level B<EVP> interface such as L<EVP_DigestSignInit(3)>
74 or L<EVP_DigestVerifyInit(3)> instead.
76 ECDSA_size() returns the maximum length of a DER encoded ECDSA signature
77 created with the private EC key I<eckey>. To obtain the actual signature
78 size use L<EVP_PKEY_sign(3)> with a NULL I<sig> parameter.
80 ECDSA_sign() computes a digital signature of the I<dgstlen> bytes hash value
81 I<dgst> using the private EC key I<eckey>. The DER encoded signatures is
82 stored in I<sig> and its length is returned in I<sig_len>. Note: I<sig> must
83 point to ECDSA_size(eckey) bytes of memory. The parameter I<type> is currently
84 ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with I<kinv>
85 and I<rp> set to NULL.
87 ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned
88 as a newly allocated B<ECDSA_SIG> structure (or NULL on error). ECDSA_do_sign()
89 is a wrapper function for ECDSA_do_sign_ex() with I<kinv> and I<rp> set to
92 ECDSA_verify() verifies that the signature in I<sig> of size I<siglen> is a
93 valid ECDSA signature of the hash value I<dgst> of size I<dgstlen> using the
94 public key I<eckey>. The parameter I<type> is ignored.
96 ECDSA_do_verify() is similar to ECDSA_verify() except the signature is
97 presented in the form of a pointer to an B<ECDSA_SIG> structure.
99 The remaining functions utilise the internal I<kinv> and I<r> values used
100 during signature computation. Most applications will never need to call these
101 and some external ECDSA ENGINE implementations may not support them at all if
102 either I<kinv> or I<r> is not NULL.
104 ECDSA_sign_setup() may be used to precompute parts of the signing operation.
105 I<eckey> is the private EC key and I<ctx> is a pointer to B<BN_CTX> structure
106 (or NULL). The precomputed values or returned in I<kinv> and I<rp> and can be
107 used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex().
109 ECDSA_sign_ex() computes a digital signature of the I<dgstlen> bytes hash value
110 I<dgst> using the private EC key I<eckey> and the optional pre-computed values
111 I<kinv> and I<rp>. The DER encoded signature is stored in I<sig> and its
112 length is returned in I<sig_len>. Note: I<sig> must point to ECDSA_size(eckey)
113 bytes of memory. The parameter I<type> is ignored.
115 ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is
116 returned as a newly allocated B<ECDSA_SIG> structure (or NULL on error).
120 ECDSA_SIG_new() returns NULL if the allocation fails.
122 ECDSA_SIG_set0() returns 1 on success or 0 on failure.
124 ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value,
125 or NULL if it is unset.
127 ECDSA_size() returns the maximum length signature or 0 on error.
129 ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful
132 ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated
133 B<ECDSA_SIG> structure or NULL on error.
135 ECDSA_verify() and ECDSA_do_verify() return 1 for a valid
136 signature, 0 for an invalid signature and -1 on error.
137 The error codes can be obtained by L<ERR_get_error(3)>.
141 Creating an ECDSA signature of a given SHA-256 hash value using the
142 named curve prime256v1 (aka P-256).
144 First step: create an EC_KEY object (note: this part is B<not> ECDSA
151 eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
154 if (EC_KEY_generate_key(eckey) == 0)
157 Second step: compute the ECDSA signature of a SHA-256 hash value
158 using ECDSA_do_sign():
160 sig = ECDSA_do_sign(digest, 32, eckey);
164 or using ECDSA_sign():
166 unsigned char *buffer, *pp;
169 buf_len = ECDSA_size(eckey);
170 buffer = OPENSSL_malloc(buf_len);
172 if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0)
175 Third step: verify the created ECDSA signature using ECDSA_do_verify():
177 ret = ECDSA_do_verify(digest, 32, sig, eckey);
179 or using ECDSA_verify():
181 ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey);
183 and finally evaluate the return value:
188 /* incorrect signature */
194 ANSI X9.62, US Federal Information Processing Standard FIPS186-2
195 (Digital Signature Standard, DSS)
200 L<EVP_DigestSignInit(3)>,
201 L<EVP_DigestVerifyInit(3)>,
208 The ECDSA_size(), ECDSA_sign(), ECDSA_do_sign(), ECDSA_verify(),
209 ECDSA_do_verify(), ECDSA_sign_setup(), ECDSA_sign_ex() and ECDSA_do_sign_ex()
210 functions were deprecated in OpenSSL 3.0.
214 Copyright 2004-2021 The OpenSSL Project Authors. All Rights Reserved.
216 Licensed under the Apache License 2.0 (the "License"). You may not use
217 this file except in compliance with the License. You can obtain a copy
218 in the file LICENSE in the source distribution or at
219 L<https://www.openssl.org/source/license.html>.