ECDSA_SIG_NEW(3) OpenSSL ECDSA_SIG_NEW(3)
NAME
ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0,
ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_size, ECDSA_sign, ECDSA_do_sign,
ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex,
ECDSA_do_sign_ex - low-level elliptic curve digital signature algorithm
(ECDSA) functions
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);
int ECDSA_size(const EC_KEY *eckey);
int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen,
unsigned char *sig, unsigned int *siglen, EC_KEY *eckey);
ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
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_do_verify(const unsigned char *dgst, int dgst_len,
const ECDSA_SIG *sig, 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_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp);
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);
DESCRIPTION
Note: these functions provide a low-level interface to ECDSA. Most
applications should use the higher level EVP interface such as
EVP_DigestSignInit(3) or EVP_DigestVerifyInit(3) instead.
ECDSA_SIG is an opaque structure consisting of two BIGNUMs for the r
and s value of an ECDSA signature (see X9.62 or FIPS 186-2).
ECDSA_SIG_new() allocates an empty ECDSA_SIG structure. Note: before
OpenSSL 1.1.0 the: the r and s components were initialised.
ECDSA_SIG_free() frees the ECDSA_SIG structure sig.
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.
The r and s values can be set by calling ECDSA_SIG_set0() and passing
the new values for r and s as parameters to the function. 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 directly after this function has been called.
See i2d_ECDSA_SIG(3) and d2i_ECDSA_SIG(3) for information about
encoding and decoding ECDSA signatures to/from DER.
ECDSA_size() returns the maximum length of a DER encoded ECDSA
signature created with the private EC key eckey.
ECDSA_sign() computes a digital signature of the dgstlen bytes hash
value dgst using the private EC key eckey. The DER encoded signatures
is stored in sig and its length is returned in sig_len. Note: sig must
point to ECDSA_size(eckey) bytes of memory. The parameter type is
currently ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex()
with kinv and rp set to NULL.
ECDSA_do_sign() is similar to ECDSA_sign() except the signature is
returned as a newly allocated ECDSA_SIG structure (or NULL on error).
ECDSA_do_sign() is a wrapper function for ECDSA_do_sign_ex() with kinv
and rp set to NULL.
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_verify() is similar to ECDSA_verify() except the signature is
presented in the form of a pointer to an ECDSA_SIG structure.
The remaining functions utilise the internal kinv and r values used
during signature computation. Most applications will never need to call
these and some external ECDSA ENGINE implementations may not support
them at all if either kinv or r is not NULL.
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_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 signature is stored in sig and its
length is returned in sig_len. Note: sig must point to
ECDSA_size(eckey) bytes of memory. The parameter type is ignored.
ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature
is returned as a newly allocated ECDSA_SIG structure (or NULL on
error).
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.
ECDSA_size() returns the maximum length signature or 0 on error.
ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if
successful or 0 on error.
ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated
ECDSA_SIG structure or NULL 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).
EXAMPLES
Creating an ECDSA signature of a given SHA-256 hash value using the
named curve prime256v1 (aka P-256).
First step: create an 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_X9_62_prime256v1);
if (eckey == NULL)
/* error */
if (EC_KEY_generate_key(eckey) == 0)
/* error */
Second step: compute the ECDSA signature of a SHA-256 hash value using
ECDSA_do_sign():
sig = ECDSA_do_sign(digest, 32, 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) == 0)
/* error */
Third step: verify the created ECDSA signature using ECDSA_do_verify():
ret = ECDSA_do_verify(digest, 32, sig, eckey);
or using ECDSA_verify():
ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey);
and finally evaluate the return value:
if (ret == 1)
/* signature ok */
else if (ret == 0)
/* incorrect signature */
else
/* error */
CONFORMING TO
ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
(Digital Signature Standard, DSS)
SEE ALSO
EC_KEY_new(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3),
i2d_ECDSA_SIG(3), d2i_ECDSA_SIG(3)
COPYRIGHT
Copyright 2004-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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>;.
1.1.1k 2021-03-25 ECDSA_SIG_NEW(3)
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