=pod =head1 NAME ecdsa - Elliptic Curve Digital Signature Algorithm =head1 SYNOPSIS #include ECDSA_SIG* ECDSA_SIG_new(void); void ECDSA_SIG_free(ECDSA_SIG *sig); int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp); ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len); ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len, EC_KEY *eckey); ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); int ECDSA_do_verify(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, EC_KEY* eckey); int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp); int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen, unsigned char *sig, unsigned int *siglen, EC_KEY *eckey); int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen, unsigned char *sig, unsigned int *siglen, const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen, const unsigned char *sig, int siglen, EC_KEY *eckey); int ECDSA_size(const EC_KEY *eckey); const ECDSA_METHOD* ECDSA_OpenSSL(void); void ECDSA_set_default_method(const ECDSA_METHOD *meth); const ECDSA_METHOD* ECDSA_get_default_method(void); int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth); int ECDSA_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func); int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg); void* ECDSA_get_ex_data(EC_KEY *d, int idx); =head1 DESCRIPTION The B structure consists of two BIGNUMs for the r and s value of a ECDSA signature (see X9.62 or FIPS 186-2). struct { BIGNUM *r; BIGNUM *s; } ECDSA_SIG; ECDSA_SIG_new() allocates a new B structure (note: this function also allocates the BIGNUMs) and initialize it. ECDSA_SIG_free() frees the B structure B. i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature B and writes the encoded signature to B<*pp> (note: if B is NULL B returns the expected length in bytes of the DER encoded signature). B returns the length of the DER encoded signature (or 0 on error). d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the decoded signature in a newly allocated B structure. B<*sig> points to the buffer containing the DER encoded signature of size B. ECDSA_size() returns the maximum length of a DER encoded ECDSA signature created with the private EC key B. ECDSA_sign_setup() may be used to precompute parts of the signing operation. B is the private EC key and B is a pointer to B structure (or NULL). The precomputed values or returned in B and B and can be used in a later call to B or B. ECDSA_sign() is wrapper function for ECDSA_sign_ex with B and B set to NULL. ECDSA_sign_ex() computes a digital signature of the B bytes hash value B using the private EC key B and the optional pre-computed values B and B. The DER encoded signatures is stored in B and it's length is returned in B. Note: B must point to B bytes of memory. The parameter B is ignored. ECDSA_verify() verifies that the signature in B of size B is a valid ECDSA signature of the hash value value B of size B using the public key B. The parameter B is ignored. ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B and B set to NULL. ECDSA_do_sign_ex() computes a digital signature of the B bytes hash value B using the private key B and the optional pre-computed values B and B. The signature is returned in a newly allocated B structure (or NULL on error). ECDSA_do_verify() verifies that the signature B is a valid ECDSA signature of the hash value B of size B using the public key B. =head1 RETURN VALUES ECDSA_size() returns the maximum length signature or 0 on error. ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0 on error. ECDSA_verify() and ECDSA_do_verify() return 1 for a valid signature, 0 for an invalid signature and -1 on error. The error codes can be obtained by L. =head1 EXAMPLES Creating a ECDSA signature of given SHA-1 hash value using the named curve secp192k1. First step: create a EC_KEY object (note: this part is B ECDSA specific) int ret; ECDSA_SIG *sig; EC_KEY *eckey = EC_KEY_new(); if (eckey == NULL) { /* error */ } key->group = EC_GROUP_new_by_nid(NID_secp192k1); if (key->group == NULL) { /* error */ } if (!EC_KEY_generate_key(eckey)) { /* error */ } Second step: compute the ECDSA signature of a SHA-1 hash value using B sig = ECDSA_do_sign(digest, 20, eckey); if (sig == NULL) { /* error */ } or using B unsigned char *buffer, *pp; int buf_len; buf_len = ECDSA_size(eckey); buffer = OPENSSL_malloc(buf_len); pp = buffer; if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey); { /* error */ } Third step: verify the created ECDSA signature using B ret = ECDSA_do_verify(digest, 20, sig, eckey); or using B ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey); and finally evaluate the return value: if (ret == -1) { /* error */ } else if (ret == 0) { /* incorrect signature */ } else /* ret == 1 */ { /* signature ok */ } =head1 CONFORMING TO ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 (Digital Signature Standard, DSS) =head1 SEE ALSO L, L =head1 HISTORY The ecdsa implementation was first introduced in OpenSSL 0.9.8 =head1 AUTHOR Nils Larsch for the OpenSSL project (http://www.openssl.org). =cut