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- =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
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