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Diffstat (limited to 'openssl/doc/crypto/ecdsa.pod')
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diff --git a/openssl/doc/crypto/ecdsa.pod b/openssl/doc/crypto/ecdsa.pod new file mode 100644 index 000000000..49b10f224 --- /dev/null +++ b/openssl/doc/crypto/ecdsa.pod @@ -0,0 +1,210 @@ +=pod + +=head1 NAME + +ecdsa - Elliptic Curve Digital Signature Algorithm + +=head1 SYNOPSIS + + #include <openssl/ecdsa.h> + + 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<ECDSA_SIG> 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<ECDSA_SIG> structure (note: this +function also allocates the BIGNUMs) and initialize it. + +ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>. + +i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature +B<sig> and writes the encoded signature to B<*pp> (note: if B<pp> +is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of +the DER encoded signature). B<i2d_ECDSA_SIG> 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<ECDSA_SIG> structure. +B<*sig> points to the buffer containing the DER encoded signature +of size B<len>. + +ECDSA_size() returns the maximum length of a DER encoded +ECDSA signature created with the private EC key B<eckey>. + +ECDSA_sign_setup() may be used to precompute parts of the +signing operation. B<eckey> is the private EC key and B<ctx> +is a pointer to B<BN_CTX> structure (or NULL). The precomputed +values or returned in B<kinv> and B<rp> and can be used in a +later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>. + +ECDSA_sign() is wrapper function for ECDSA_sign_ex with B<kinv> +and B<rp> set to NULL. + +ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes +hash value B<dgst> using the private EC key B<eckey> and the optional +pre-computed values B<kinv> and B<rp>. The DER encoded signatures is +stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig> +must point to B<ECDSA_size> bytes of memory. The parameter B<type> +is ignored. + +ECDSA_verify() verifies that the signature in B<sig> of size +B<siglen> is a valid ECDSA signature of the hash value +value B<dgst> of size B<dgstlen> using the public key B<eckey>. +The parameter B<type> is ignored. + +ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv> +and B<rp> set to NULL. + +ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len> +bytes hash value B<dgst> using the private key B<eckey> and the +optional pre-computed values B<kinv> and B<rp>. The signature is +returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error). + +ECDSA_do_verify() verifies that the signature B<sig> is a valid +ECDSA signature of the hash value B<dgst> of size B<dgst_len> +using the public key B<eckey>. + +=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 -1 +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<ERR_get_error(3)|ERR_get_error(3)>. + +=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<not> 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<ECDSA_do_sign> + + sig = ECDSA_do_sign(digest, 20, eckey); + if (sig == NULL) + { + /* error */ + } + +or using B<ECDSA_sign> + + 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<ECDSA_do_verify> + + ret = ECDSA_do_verify(digest, 20, sig, eckey); + +or using B<ECDSA_verify> + + 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<dsa(3)|dsa(3)>, L<rsa(3)|rsa(3)> + +=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 |