1=pod 2 3=head1 NAME 4 5ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0, 6ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_size, ECDSA_sign, ECDSA_do_sign, 7ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex, 8ECDSA_do_sign_ex - low-level elliptic curve digital signature algorithm (ECDSA) 9functions 10 11=head1 SYNOPSIS 12 13 #include <openssl/ecdsa.h> 14 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); 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); 40 41=head1 DESCRIPTION 42 43Note: these functions provide a low-level interface to ECDSA. Most 44applications should use the higher level B<EVP> interface such as 45L<EVP_DigestSignInit(3)> or L<EVP_DigestVerifyInit(3)> instead. 46 47B<ECDSA_SIG> is an opaque structure consisting of two BIGNUMs for the 48B<r> and B<s> value of an ECDSA signature (see X9.62 or FIPS 186-2). 49 50ECDSA_SIG_new() allocates an empty B<ECDSA_SIG> structure. Note: before 51OpenSSL 1.1.0 the: the B<r> and B<s> components were initialised. 52 53ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>. 54 55ECDSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained 56in B<sig> and stores them in B<*pr> and B<*ps>, respectively. 57The pointer B<pr> or B<ps> can be NULL, in which case the corresponding value 58is not returned. 59 60The values B<r>, B<s> can also be retrieved separately by the corresponding 61function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively. 62 63The B<r> and B<s> values can be set by calling ECDSA_SIG_set0() and passing the 64new values for B<r> and B<s> as parameters to the function. Calling this 65function transfers the memory management of the values to the ECDSA_SIG object, 66and therefore the values that have been passed in should not be freed directly 67after this function has been called. 68 69See L<i2d_ECDSA_SIG(3)> and L<d2i_ECDSA_SIG(3)> for information about encoding 70and decoding ECDSA signatures to/from DER. 71 72ECDSA_size() returns the maximum length of a DER encoded ECDSA signature 73created with the private EC key B<eckey>. 74 75ECDSA_sign() computes a digital signature of the B<dgstlen> bytes hash value 76B<dgst> using the private EC key B<eckey>. The DER encoded signatures is 77stored in B<sig> and its length is returned in B<sig_len>. Note: B<sig> must 78point to ECDSA_size(eckey) bytes of memory. The parameter B<type> is currently 79ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with B<kinv> 80and B<rp> set to NULL. 81 82ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned 83as a newly allocated B<ECDSA_SIG> structure (or NULL on error). ECDSA_do_sign() 84is a wrapper function for ECDSA_do_sign_ex() with B<kinv> and B<rp> set to 85NULL. 86 87ECDSA_verify() verifies that the signature in B<sig> of size B<siglen> is a 88valid ECDSA signature of the hash value B<dgst> of size B<dgstlen> using the 89public key B<eckey>. The parameter B<type> is ignored. 90 91ECDSA_do_verify() is similar to ECDSA_verify() except the signature is 92presented in the form of a pointer to an B<ECDSA_SIG> structure. 93 94The remaining functions utilise the internal B<kinv> and B<r> values used 95during signature computation. Most applications will never need to call these 96and some external ECDSA ENGINE implementations may not support them at all if 97either B<kinv> or B<r> is not B<NULL>. 98 99ECDSA_sign_setup() may be used to precompute parts of the signing operation. 100B<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 102used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex(). 103 104ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes hash value 105B<dgst> using the private EC key B<eckey> and the optional pre-computed values 106B<kinv> and B<rp>. The DER encoded signature is stored in B<sig> and its 107length is returned in B<sig_len>. Note: B<sig> must point to ECDSA_size(eckey) 108bytes of memory. The parameter B<type> is ignored. 109 110ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is 111returned as a newly allocated B<ECDSA_SIG> structure (or NULL on error). 112 113=head1 RETURN VALUES 114 115ECDSA_SIG_new() returns NULL if the allocation fails. 116 117ECDSA_SIG_set0() returns 1 on success or 0 on failure. 118 119ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, 120or NULL if it is unset. 121 122ECDSA_size() returns the maximum length signature or 0 on error. 123 124ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful 125or 0 on error. 126 127ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated 128B<ECDSA_SIG> structure or NULL on error. 129 130ECDSA_verify() and ECDSA_do_verify() return 1 for a valid 131signature, 0 for an invalid signature and -1 on error. 132The error codes can be obtained by L<ERR_get_error(3)>. 133 134=head1 EXAMPLES 135 136Creating an ECDSA signature of a given SHA-256 hash value using the 137named curve prime256v1 (aka P-256). 138 139First step: create an EC_KEY object (note: this part is B<not> ECDSA 140specific) 141 142 int ret; 143 ECDSA_SIG *sig; 144 EC_KEY *eckey; 145 146 eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1); 147 if (eckey == NULL) 148 /* error */ 149 if (EC_KEY_generate_key(eckey) == 0) 150 /* error */ 151 152Second step: compute the ECDSA signature of a SHA-256 hash value 153using ECDSA_do_sign(): 154 155 sig = ECDSA_do_sign(digest, 32, eckey); 156 if (sig == NULL) 157 /* error */ 158 159or using ECDSA_sign(): 160 161 unsigned char *buffer, *pp; 162 int buf_len; 163 164 buf_len = ECDSA_size(eckey); 165 buffer = OPENSSL_malloc(buf_len); 166 pp = buffer; 167 if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0) 168 /* error */ 169 170Third step: verify the created ECDSA signature using ECDSA_do_verify(): 171 172 ret = ECDSA_do_verify(digest, 32, sig, eckey); 173 174or using ECDSA_verify(): 175 176 ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); 177 178and finally evaluate the return value: 179 180 if (ret == 1) 181 /* signature ok */ 182 else if (ret == 0) 183 /* incorrect signature */ 184 else 185 /* error */ 186 187=head1 CONFORMING TO 188 189ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 190(Digital Signature Standard, DSS) 191 192=head1 SEE ALSO 193 194L<EC_KEY_new(3)>, 195L<EVP_DigestSignInit(3)>, 196L<EVP_DigestVerifyInit(3)>, 197L<i2d_ECDSA_SIG(3)>, 198L<d2i_ECDSA_SIG(3)> 199 200=head1 COPYRIGHT 201 202Copyright 2004-2020 The OpenSSL Project Authors. All Rights Reserved. 203 204Licensed under the OpenSSL license (the "License"). You may not use 205this file except in compliance with the License. You can obtain a copy 206in the file LICENSE in the source distribution or at 207L<https://www.openssl.org/source/license.html>. 208 209=cut 210