ECDSA_SIG_NEW - Online Linux Manual PageSection : 3
Updated : 2021-03-26
Source : 1.1.1k
Note : OpenSSL

NAMEECDSA_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);

DESCRIPTIONNote: 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 VALUESECDSA_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).

EXAMPLESCreating 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 TOANSI X9.62, US Federal Information Processing Standard FIPS 186−2 (Digital Signature Standard, DSS)

SEE ALSOEC_KEY_new(3), ​EVP_DigestSignInit(3), ​EVP_DigestVerifyInit(3), ​i2d_ECDSA_SIG(3), ​d2i_ECDSA_SIG(3)

COPYRIGHTCopyright 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>.
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