ecdsa(3) | OpenSSL | ecdsa(3) |
struct
{
BIGNUM *r;
BIGNUM *s;
} ECDSA_SIG;
ECDSA_SIG_new() allocates a new ECDSA_SIG structure (note: this function also allocates the BIGNUMs) and initialize it.
ECDSA_SIG_free() frees the ECDSA_SIG structure sig.
i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature sig and writes the encoded signature to *pp (note: if pp is NULL i2d_ECDSA_SIG returns the expected length in bytes of the DER encoded signature). 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 ECDSA_SIG structure. *sig points to the buffer containing the DER encoded signature of size len.
ECDSA_size() returns the maximum length of a DER encoded ECDSA signature created with the private EC key eckey.
ECDSA_sign_setup() may be used to precompute parts of the signing operation. eckey is the private EC key and ctx is a pointer to BN_CTX structure (or NULL). The precomputed values or returned in kinv and rp and can be used in a later call to ECDSA_sign_ex or ECDSA_do_sign_ex.
ECDSA_sign() is wrapper function for ECDSA_sign_ex with kinv and rp set to NULL.
ECDSA_sign_ex() computes a digital signature of the dgstlen bytes hash value dgst using the private EC key eckey and the optional pre-computed values kinv and rp. The DER encoded signatures is stored in sig and it's length is returned in sig_len. Note: sig must point to ECDSA_size bytes of memory. The parameter type is ignored.
ECDSA_verify() verifies that the signature in sig of size siglen is a valid ECDSA signature of the hash value dgst of size dgstlen using the public key eckey. The parameter type is ignored.
ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with kinv and rp set to NULL.
ECDSA_do_sign_ex() computes a digital signature of the dgst_len bytes hash value dgst using the private key eckey and the optional pre-computed values kinv and rp. The signature is returned in a newly allocated ECDSA_SIG structure (or NULL on error).
ECDSA_do_verify() verifies that the signature sig is a valid ECDSA signature of the hash value dgst of size dgst_len using the public key eckey.
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 ERR_get_error(3).
First step: create a EC_KEY object (note: this part is not ECDSA specific)
int ret;
ECDSA_SIG *sig;
EC_KEY *eckey;
eckey = EC_KEY_new_by_curve_name(NID_secp192k1);
if (eckey == NULL)
{
/* error */
}
if (!EC_KEY_generate_key(eckey))
{
/* error */
}
Second step: compute the ECDSA signature of a SHA-1 hash value using ECDSA_do_sign
sig = ECDSA_do_sign(digest, 20, eckey);
if (sig == NULL)
{
/* error */
}
or using 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 ECDSA_do_verify
ret = ECDSA_do_verify(digest, 20, sig, eckey);
or using 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 */
}
2014-01-11 | 1.0.1u |