1=pod 2 3=head1 NAME 4 5ecdsa - Elliptic Curve Digital Signature Algorithm 6 7=head1 SYNOPSIS 8 9 #include <openssl/ecdsa.h> 10 11 ECDSA_SIG* ECDSA_SIG_new(void); 12 void ECDSA_SIG_free(ECDSA_SIG *sig); 13 int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp); 14 ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, 15 long len); 16 17 ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len, 18 EC_KEY *eckey); 19 ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, 20 const BIGNUM *kinv, const BIGNUM *rp, 21 EC_KEY *eckey); 22 int ECDSA_do_verify(const unsigned char *dgst, int dgst_len, 23 const ECDSA_SIG *sig, EC_KEY* eckey); 24 int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, 25 BIGNUM **kinv, BIGNUM **rp); 26 int ECDSA_sign(int type, const unsigned char *dgst, 27 int dgstlen, unsigned char *sig, 28 unsigned int *siglen, EC_KEY *eckey); 29 int ECDSA_sign_ex(int type, const unsigned char *dgst, 30 int dgstlen, unsigned char *sig, 31 unsigned int *siglen, const BIGNUM *kinv, 32 const BIGNUM *rp, EC_KEY *eckey); 33 int ECDSA_verify(int type, const unsigned char *dgst, 34 int dgstlen, const unsigned char *sig, 35 int siglen, EC_KEY *eckey); 36 int ECDSA_size(const EC_KEY *eckey); 37 38 const ECDSA_METHOD* ECDSA_OpenSSL(void); 39 void ECDSA_set_default_method(const ECDSA_METHOD *meth); 40 const ECDSA_METHOD* ECDSA_get_default_method(void); 41 int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth); 42 43 int ECDSA_get_ex_new_index(long argl, void *argp, 44 CRYPTO_EX_new *new_func, 45 CRYPTO_EX_dup *dup_func, 46 CRYPTO_EX_free *free_func); 47 int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg); 48 void* ECDSA_get_ex_data(EC_KEY *d, int idx); 49 50=head1 DESCRIPTION 51 52The B<ECDSA_SIG> structure consists of two BIGNUMs for the 53r and s value of a ECDSA signature (see X9.62 or FIPS 186-2). 54 55 struct 56 { 57 BIGNUM *r; 58 BIGNUM *s; 59 } ECDSA_SIG; 60 61ECDSA_SIG_new() allocates a new B<ECDSA_SIG> structure (note: this 62function also allocates the BIGNUMs) and initialize it. 63 64ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>. 65 66i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature 67B<sig> and writes the encoded signature to B<*pp> (note: if B<pp> 68is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of 69the DER encoded signature). B<i2d_ECDSA_SIG> returns the length 70of the DER encoded signature (or 0 on error). 71 72d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns 73the decoded signature in a newly allocated B<ECDSA_SIG> structure. 74B<*sig> points to the buffer containing the DER encoded signature 75of size B<len>. 76 77ECDSA_size() returns the maximum length of a DER encoded 78ECDSA signature created with the private EC key B<eckey>. 79 80ECDSA_sign_setup() may be used to precompute parts of the 81signing operation. B<eckey> is the private EC key and B<ctx> 82is a pointer to B<BN_CTX> structure (or NULL). The precomputed 83values or returned in B<kinv> and B<rp> and can be used in a 84later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>. 85 86ECDSA_sign() is wrapper function for ECDSA_sign_ex with B<kinv> 87and B<rp> set to NULL. 88 89ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes 90hash value B<dgst> using the private EC key B<eckey> and the optional 91pre-computed values B<kinv> and B<rp>. The DER encoded signatures is 92stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig> 93must point to B<ECDSA_size> bytes of memory. The parameter B<type> 94is ignored. 95 96ECDSA_verify() verifies that the signature in B<sig> of size 97B<siglen> is a valid ECDSA signature of the hash value 98B<dgst> of size B<dgstlen> using the public key B<eckey>. 99The parameter B<type> is ignored. 100 101ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv> 102and B<rp> set to NULL. 103 104ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len> 105bytes hash value B<dgst> using the private key B<eckey> and the 106optional pre-computed values B<kinv> and B<rp>. The signature is 107returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error). 108 109ECDSA_do_verify() verifies that the signature B<sig> is a valid 110ECDSA signature of the hash value B<dgst> of size B<dgst_len> 111using the public key B<eckey>. 112 113=head1 RETURN VALUES 114 115ECDSA_size() returns the maximum length signature or 0 on error. 116 117ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0 118on error. 119 120ECDSA_verify() and ECDSA_do_verify() return 1 for a valid 121signature, 0 for an invalid signature and -1 on error. 122The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 123 124=head1 EXAMPLES 125 126Creating a ECDSA signature of given SHA-1 hash value using the 127named curve secp192k1. 128 129First step: create a EC_KEY object (note: this part is B<not> ECDSA 130specific) 131 132 int ret; 133 ECDSA_SIG *sig; 134 EC_KEY *eckey; 135 eckey = EC_KEY_new_by_curve_name(NID_secp192k1); 136 if (eckey == NULL) 137 { 138 /* error */ 139 } 140 if (!EC_KEY_generate_key(eckey)) 141 { 142 /* error */ 143 } 144 145Second step: compute the ECDSA signature of a SHA-1 hash value 146using B<ECDSA_do_sign> 147 148 sig = ECDSA_do_sign(digest, 20, eckey); 149 if (sig == NULL) 150 { 151 /* error */ 152 } 153 154or using B<ECDSA_sign> 155 156 unsigned char *buffer, *pp; 157 int buf_len; 158 buf_len = ECDSA_size(eckey); 159 buffer = OPENSSL_malloc(buf_len); 160 pp = buffer; 161 if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey); 162 { 163 /* error */ 164 } 165 166Third step: verify the created ECDSA signature using B<ECDSA_do_verify> 167 168 ret = ECDSA_do_verify(digest, 20, sig, eckey); 169 170or using B<ECDSA_verify> 171 172 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey); 173 174and finally evaluate the return value: 175 176 if (ret == -1) 177 { 178 /* error */ 179 } 180 else if (ret == 0) 181 { 182 /* incorrect signature */ 183 } 184 else /* ret == 1 */ 185 { 186 /* signature ok */ 187 } 188 189=head1 CONFORMING TO 190 191ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 192(Digital Signature Standard, DSS) 193 194=head1 SEE ALSO 195 196L<dsa(3)|dsa(3)>, L<rsa(3)|rsa(3)> 197 198=head1 HISTORY 199 200The ecdsa implementation was first introduced in OpenSSL 0.9.8 201 202=head1 AUTHOR 203 204Nils Larsch for the OpenSSL project (http://www.openssl.org). 205 206=cut 207