NAME

ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0 - Functions for creating, destroying and manipulating ECDSA_SIG objects

SYNOPSIS

#include <openssl/ecdsa.h>

ECDSA_SIG *ECDSA_SIG_new(void);
void ECDSA_SIG_free(ECDSA_SIG *sig);
void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);

DESCRIPTION

ECDSA_SIG is an opaque structure consisting of two BIGNUMs for the r and s value of an Elliptic Curve Digital Signature Algorithm (ECDSA) signature (see FIPS186-4 or X9.62). The ECDSA_SIG object was mainly used by the deprecated low level functions described in ECDSA_sign(3), it is still required in order to be able to set or get the values of r and s into or from a signature. This is mainly used for testing purposes as shown in the "EXAMPLES".

ECDSA_SIG_new() allocates an empty ECDSA_SIG structure. Note: before OpenSSL 1.1.0, the r and s components were initialised.

ECDSA_SIG_free() frees the ECDSA_SIG structure sig. If the argument is NULL, nothing is done.

ECDSA_SIG_get0() returns internal pointers the r and s values contained in sig and stores them in *pr and *ps, respectively. The pointer pr or ps can be NULL, in which case the corresponding value is not returned.

The values r, s can also be retrieved separately by the corresponding function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively.

Non-NULL r and s values can be set on the sig by calling ECDSA_SIG_set0(). Calling this function transfers the memory management of the values to the ECDSA_SIG object, and therefore the values that have been passed in should not be freed by the caller.

See i2d_ECDSA_SIG(3) and d2i_ECDSA_SIG(3) for information about encoding and decoding ECDSA signatures to/from DER.

RETURN VALUES

ECDSA_SIG_new() returns NULL if the allocation fails.

ECDSA_SIG_set0() returns 1 on success or 0 on failure.

ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, or NULL if it is unset.

EXAMPLES

Extract signature r and s values from a ECDSA signature of size signaturelen:

ECDSA_SIG *obj;
const BIGNUM *r, *s;

/* Load a signature into the ECDSA_SIG object */
obj = d2i_ECDSA_SIG(NULL, &signature, signaturelen);
if (obj == NULL)
    /* error */

r = ECDSA_SIG_get0_r(obj);
s = ECDSA_SIG_get0_s(obj);
if (r == NULL || s == NULL)
    /* error */

/* Use BN_bn2binpad() here to convert to r and s into byte arrays */

/*
 * Do not try to access I<r> or I<s> after calling ECDSA_SIG_free(),
 * as they are both freed by this call.
 */
ECDSA_SIG_free(obj);

Convert r and s byte arrays into an ECDSA_SIG signature of size signaturelen:

ECDSA_SIG *obj = NULL;
unsigned char *signature = NULL;
size_t signaturelen;
BIGNUM *rbn = NULL, *sbn = NULL;

obj = ECDSA_SIG_new();
if (obj == NULL)
    /* error */
rbn = BN_bin2bn(r, rlen, NULL);
sbn = BN_bin2bn(s, slen, NULL);
if (rbn == NULL || sbn == NULL)
    /* error */

if (!ECDSA_SIG_set0(obj, rbn, sbn))
    /* error */
/* Set these to NULL since they are now owned by obj */
rbn = sbn = NULL;

signaturelen = i2d_ECDSA_SIG(obj, &signature);
if (signaturelen <= 0)
    /* error */

/*
 * This signature could now be passed to L<EVP_DigestVerify(3)>
 * or L<EVP_DigestVerifyFinal(3)>
 */

BN_free(rbn);
BN_free(sbn);
OPENSSL_free(signature);
ECDSA_SIG_free(obj);

CONFORMING TO

ANSI X9.62, US Federal Information Processing Standard FIPS186-4 (Digital Signature Standard, DSS)

COPYRIGHT

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.