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Editing: ECDSA_sign_ex.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" Note: these functions provide a low-level interface to \s-1ECDSA.\s0 Most applications should use the higher level \fB\s-1EVP\s0\fR interface such as \&\fBEVP_DigestSignInit\fR\|(3) or \fBEVP_DigestVerifyInit\fR\|(3) instead. .PP \&\fB\s-1ECDSA_SIG\s0\fR is an opaque structure consisting of two BIGNUMs for the \&\fBr\fR and \fBs\fR value of an \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS 186\-2\s0). .PP \&\fBECDSA_SIG_new()\fR allocates an empty \fB\s-1ECDSA_SIG\s0\fR structure. Note: before OpenSSL 1.1.0 the: the \fBr\fR and \fBs\fR components were initialised. .PP \&\fBECDSA_SIG_free()\fR frees the \fB\s-1ECDSA_SIG\s0\fR structure \fBsig\fR. .PP \&\fBECDSA_SIG_get0()\fR returns internal pointers the \fBr\fR and \fBs\fR values contained in \fBsig\fR and stores them in \fB*pr\fR and \fB*ps\fR, respectively. The pointer \fBpr\fR or \fBps\fR can be \s-1NULL,\s0 in which case the corresponding value is not returned. .PP The values \fBr\fR, \fBs\fR can also be retrieved separately by the corresponding function \fBECDSA_SIG_get0_r()\fR and \fBECDSA_SIG_get0_s()\fR, respectively. .PP The \fBr\fR and \fBs\fR values can be set by calling \fBECDSA_SIG_set0()\fR and passing the new values for \fBr\fR and \fBs\fR as parameters to the function. Calling this function transfers the memory management of the values to the \s-1ECDSA_SIG\s0 object, and therefore the values that have been passed in should not be freed directly after this function has been called. .PP See \fBi2d_ECDSA_SIG\fR\|(3) and \fBd2i_ECDSA_SIG\fR\|(3) for information about encoding and decoding \s-1ECDSA\s0 signatures to/from \s-1DER.\s0 .PP \&\fBECDSA_size()\fR returns the maximum length of a \s-1DER\s0 encoded \s-1ECDSA\s0 signature created with the private \s-1EC\s0 key \fBeckey\fR. .PP \&\fBECDSA_sign()\fR computes a digital signature of the \fBdgstlen\fR bytes hash value \&\fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR. The \s-1DER\s0 encoded signatures is stored in \fBsig\fR and its length is returned in \fBsig_len\fR. Note: \fBsig\fR must point to ECDSA_size(eckey) bytes of memory. The parameter \fBtype\fR is currently ignored. \fBECDSA_sign()\fR is wrapper function for \fBECDSA_sign_ex()\fR with \fBkinv\fR and \fBrp\fR set to \s-1NULL.\s0 .PP \&\fBECDSA_do_sign()\fR is similar to \fBECDSA_sign()\fR except the signature is returned as a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error). \fBECDSA_do_sign()\fR is a wrapper function for \fBECDSA_do_sign_ex()\fR with \fBkinv\fR and \fBrp\fR set to \&\s-1NULL.\s0 .PP \&\fBECDSA_verify()\fR verifies that the signature in \fBsig\fR of size \fBsiglen\fR is a valid \s-1ECDSA\s0 signature of the hash value \fBdgst\fR of size \fBdgstlen\fR using the public key \fBeckey\fR. The parameter \fBtype\fR is ignored. .PP \&\fBECDSA_do_verify()\fR is similar to \fBECDSA_verify()\fR except the signature is presented in the form of a pointer to an \fB\s-1ECDSA_SIG\s0\fR structure. .PP The remaining functions utilise the internal \fBkinv\fR and \fBr\fR values used during signature computation. Most applications will never need to call these and some external \s-1ECDSA ENGINE\s0 implementations may not support them at all if either \fBkinv\fR or \fBr\fR is not \fB\s-1NULL\s0\fR. .PP \&\fBECDSA_sign_setup()\fR may be used to precompute parts of the signing operation. \&\fBeckey\fR is the private \s-1EC\s0 key and \fBctx\fR is a pointer to \fB\s-1BN_CTX\s0\fR structure (or \s-1NULL\s0). The precomputed values or returned in \fBkinv\fR and \fBrp\fR and can be used in a later call to \fBECDSA_sign_ex()\fR or \fBECDSA_do_sign_ex()\fR. .PP \&\fBECDSA_sign_ex()\fR computes a digital signature of the \fBdgstlen\fR bytes hash value \&\fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR and the optional pre-computed values \&\fBkinv\fR and \fBrp\fR. The \s-1DER\s0 encoded signature is stored in \fBsig\fR and its length is returned in \fBsig_len\fR. Note: \fBsig\fR must point to ECDSA_size(eckey) bytes of memory. The parameter \fBtype\fR is ignored. .PP \&\fBECDSA_do_sign_ex()\fR is similar to \fBECDSA_sign_ex()\fR except the signature is returned as a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error). .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBECDSA_SIG_new()\fR returns \s-1NULL\s0 if the allocation fails. .PP \&\fBECDSA_SIG_set0()\fR returns 1 on success or 0 on failure. .PP \&\fBECDSA_SIG_get0_r()\fR and \fBECDSA_SIG_get0_s()\fR return the corresponding value, or \s-1NULL\s0 if it is unset. .PP \&\fBECDSA_size()\fR returns the maximum length signature or 0 on error. .PP \&\fBECDSA_sign()\fR, \fBECDSA_sign_ex()\fR and \fBECDSA_sign_setup()\fR return 1 if successful or 0 on error. .PP \&\fBECDSA_do_sign()\fR and \fBECDSA_do_sign_ex()\fR return a pointer to an allocated \&\fB\s-1ECDSA_SIG\s0\fR structure or \s-1NULL\s0 on error. .PP \&\fBECDSA_verify()\fR and \fBECDSA_do_verify()\fR return 1 for a valid signature, 0 for an invalid signature and \-1 on error. The error codes can be obtained by \fBERR_get_error\fR\|(3). .SH "EXAMPLES" .IX Header "EXAMPLES" Creating an \s-1ECDSA\s0 signature of a given \s-1SHA\-256\s0 hash value using the named curve prime256v1 (aka P\-256). .PP First step: create an \s-1EC_KEY\s0 object (note: this part is \fBnot\fR \s-1ECDSA\s0 specific) .PP .Vb 3 \& 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 */ .Ve .PP Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA\-256\s0 hash value using \fBECDSA_do_sign()\fR: .PP .Vb 3 \& sig = ECDSA_do_sign(digest, 32, eckey); \& if (sig == NULL) \& /* error */ .Ve .PP or using \fBECDSA_sign()\fR: .PP .Vb 2 \& 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 */ .Ve .PP Third step: verify the created \s-1ECDSA\s0 signature using \fBECDSA_do_verify()\fR: .PP .Vb 1 \& ret = ECDSA_do_verify(digest, 32, sig, eckey); .Ve .PP or using \fBECDSA_verify()\fR: .PP .Vb 1 \& ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); .Ve .PP and finally evaluate the return value: .PP .Vb 6 \& if (ret == 1) \& /* signature ok */ \& else if (ret == 0) \& /* incorrect signature */ \& else \& /* error */ .Ve .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1ANSI X9.62, US\s0 Federal Information Processing Standard \s-1FIPS 186\-2\s0 (Digital Signature Standard, \s-1DSS\s0) .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBEC_KEY_new\fR\|(3), \&\fBEVP_DigestSignInit\fR\|(3), \&\fBEVP_DigestVerifyInit\fR\|(3), \&\fBi2d_ECDSA_SIG\fR\|(3), \&\fBd2i_ECDSA_SIG\fR\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2004\-2020 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.
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