#include <openssl/ecdsa.h>
The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):
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);
See i2d_ECDSA_SIG(3) and d2i_ECDSA_SIG(3) for information about encoding and decoding ECDSA signatures to/from DER.
All of the functions described below are deprecated. Applications should use the higher level EVP interface such as EVP_DigestSignInit(3) or EVP_DigestVerifyInit(3) instead.
ECDSA_size() returns the maximum length of a DER encoded ECDSA signature created with the private EC key eckey. To obtain the actual signature size use EVP_PKEY_sign(3) with a NULL sig parameter.
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).
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).
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 */
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>.