341 lines
11 KiB
Groff
341 lines
11 KiB
Groff
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.\" ========================================================================
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.\"
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.IX Title "ecdsa 3"
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.TH ecdsa 3 "2014-08-06" "1.0.1i" "OpenSSL"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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ecdsa \- Elliptic Curve Digital Signature Algorithm
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/ecdsa.h>
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\&
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\& ECDSA_SIG* ECDSA_SIG_new(void);
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\& void ECDSA_SIG_free(ECDSA_SIG *sig);
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\& int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
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\& ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
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\& long len);
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\&
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\& ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
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\& EC_KEY *eckey);
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\& ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
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\& const BIGNUM *kinv, const BIGNUM *rp,
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\& EC_KEY *eckey);
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\& int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
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\& const ECDSA_SIG *sig, EC_KEY* eckey);
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\& int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
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\& BIGNUM **kinv, BIGNUM **rp);
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\& int ECDSA_sign(int type, const unsigned char *dgst,
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\& int dgstlen, unsigned char *sig,
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\& unsigned int *siglen, EC_KEY *eckey);
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\& int ECDSA_sign_ex(int type, const unsigned char *dgst,
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\& int dgstlen, unsigned char *sig,
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\& unsigned int *siglen, const BIGNUM *kinv,
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\& const BIGNUM *rp, EC_KEY *eckey);
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\& int ECDSA_verify(int type, const unsigned char *dgst,
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\& int dgstlen, const unsigned char *sig,
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\& int siglen, EC_KEY *eckey);
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\& int ECDSA_size(const EC_KEY *eckey);
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\&
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\& const ECDSA_METHOD* ECDSA_OpenSSL(void);
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\& void ECDSA_set_default_method(const ECDSA_METHOD *meth);
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\& const ECDSA_METHOD* ECDSA_get_default_method(void);
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\& int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
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\&
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\& int ECDSA_get_ex_new_index(long argl, void *argp,
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\& CRYPTO_EX_new *new_func,
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\& CRYPTO_EX_dup *dup_func,
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\& CRYPTO_EX_free *free_func);
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\& int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
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\& void* ECDSA_get_ex_data(EC_KEY *d, int idx);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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The \fB\s-1ECDSA_SIG\s0\fR structure consists of two BIGNUMs for the
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r and s value of a \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS\s0 186\-2).
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.PP
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.Vb 5
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\& struct
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\& {
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\& BIGNUM *r;
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\& BIGNUM *s;
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\& } ECDSA_SIG;
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.Ve
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.PP
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\&\fIECDSA_SIG_new()\fR allocates a new \fB\s-1ECDSA_SIG\s0\fR structure (note: this
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function also allocates the BIGNUMs) and initialize it.
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.PP
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\&\fIECDSA_SIG_free()\fR frees the \fB\s-1ECDSA_SIG\s0\fR structure \fBsig\fR.
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.PP
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\&\fIi2d_ECDSA_SIG()\fR creates the \s-1DER\s0 encoding of the \s-1ECDSA\s0 signature
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\&\fBsig\fR and writes the encoded signature to \fB*pp\fR (note: if \fBpp\fR
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is \s-1NULL\s0 \fBi2d_ECDSA_SIG\fR returns the expected length in bytes of
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the \s-1DER\s0 encoded signature). \fBi2d_ECDSA_SIG\fR returns the length
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of the \s-1DER\s0 encoded signature (or 0 on error).
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.PP
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\&\fId2i_ECDSA_SIG()\fR decodes a \s-1DER\s0 encoded \s-1ECDSA\s0 signature and returns
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the decoded signature in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure.
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\&\fB*sig\fR points to the buffer containing the \s-1DER\s0 encoded signature
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of size \fBlen\fR.
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.PP
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\&\fIECDSA_size()\fR returns the maximum length of a \s-1DER\s0 encoded
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\&\s-1ECDSA\s0 signature created with the private \s-1EC\s0 key \fBeckey\fR.
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.PP
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\&\fIECDSA_sign_setup()\fR may be used to precompute parts of the
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signing operation. \fBeckey\fR is the private \s-1EC\s0 key and \fBctx\fR
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is a pointer to \fB\s-1BN_CTX\s0\fR structure (or \s-1NULL\s0). The precomputed
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values or returned in \fBkinv\fR and \fBrp\fR and can be used in a
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later call to \fBECDSA_sign_ex\fR or \fBECDSA_do_sign_ex\fR.
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.PP
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\&\fIECDSA_sign()\fR is wrapper function for ECDSA_sign_ex with \fBkinv\fR
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and \fBrp\fR set to \s-1NULL\s0.
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.PP
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\&\fIECDSA_sign_ex()\fR computes a digital signature of the \fBdgstlen\fR bytes
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hash value \fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR and the optional
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pre-computed values \fBkinv\fR and \fBrp\fR. The \s-1DER\s0 encoded signatures is
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stored in \fBsig\fR and it's length is returned in \fBsig_len\fR. Note: \fBsig\fR
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must point to \fBECDSA_size\fR bytes of memory. The parameter \fBtype\fR
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is ignored.
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.PP
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\&\fIECDSA_verify()\fR verifies that the signature in \fBsig\fR of size
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\&\fBsiglen\fR is a valid \s-1ECDSA\s0 signature of the hash value
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\&\fBdgst\fR of size \fBdgstlen\fR using the public key \fBeckey\fR.
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The parameter \fBtype\fR is ignored.
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.PP
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\&\fIECDSA_do_sign()\fR is wrapper function for ECDSA_do_sign_ex with \fBkinv\fR
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and \fBrp\fR set to \s-1NULL\s0.
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.PP
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\&\fIECDSA_do_sign_ex()\fR computes a digital signature of the \fBdgst_len\fR
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bytes hash value \fBdgst\fR using the private key \fBeckey\fR and the
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optional pre-computed values \fBkinv\fR and \fBrp\fR. The signature is
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returned in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error).
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.PP
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\&\fIECDSA_do_verify()\fR verifies that the signature \fBsig\fR is a valid
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\&\s-1ECDSA\s0 signature of the hash value \fBdgst\fR of size \fBdgst_len\fR
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using the public key \fBeckey\fR.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fIECDSA_size()\fR returns the maximum length signature or 0 on error.
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.PP
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\&\fIECDSA_sign_setup()\fR and \fIECDSA_sign()\fR return 1 if successful or 0
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on error.
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.PP
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\&\fIECDSA_verify()\fR and \fIECDSA_do_verify()\fR return 1 for a valid
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signature, 0 for an invalid signature and \-1 on error.
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The error codes can be obtained by \fIERR_get_error\fR\|(3).
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.SH "EXAMPLES"
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.IX Header "EXAMPLES"
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Creating a \s-1ECDSA\s0 signature of given \s-1SHA\-1\s0 hash value using the
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named curve secp192k1.
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.PP
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First step: create a \s-1EC_KEY\s0 object (note: this part is \fBnot\fR \s-1ECDSA\s0
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specific)
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.PP
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.Vb 12
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\& int ret;
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\& ECDSA_SIG *sig;
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\& EC_KEY *eckey;
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\& eckey = EC_KEY_new_by_curve_name(NID_secp192k1);
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\& if (eckey == NULL)
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\& {
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\& /* error */
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\& }
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\& if (!EC_KEY_generate_key(eckey))
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\& {
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\& /* error */
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\& }
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.Ve
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.PP
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Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA\-1\s0 hash value
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using \fBECDSA_do_sign\fR
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.PP
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.Vb 5
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\& sig = ECDSA_do_sign(digest, 20, eckey);
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\& if (sig == NULL)
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\& {
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\& /* error */
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\& }
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.Ve
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.PP
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or using \fBECDSA_sign\fR
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.PP
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.Vb 9
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\& unsigned char *buffer, *pp;
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\& int buf_len;
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\& buf_len = ECDSA_size(eckey);
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\& buffer = OPENSSL_malloc(buf_len);
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\& pp = buffer;
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\& if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
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\& {
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\& /* error */
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\& }
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.Ve
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.PP
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Third step: verify the created \s-1ECDSA\s0 signature using \fBECDSA_do_verify\fR
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.PP
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.Vb 1
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\& ret = ECDSA_do_verify(digest, 20, sig, eckey);
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.Ve
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.PP
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or using \fBECDSA_verify\fR
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.PP
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.Vb 1
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\& ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
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.Ve
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.PP
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and finally evaluate the return value:
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.PP
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.Vb 12
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\& if (ret == \-1)
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\& {
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\& /* error */
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\& }
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\& else if (ret == 0)
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\& {
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\& /* incorrect signature */
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\& }
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\& else /* ret == 1 */
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\& {
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\& /* signature ok */
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\& }
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.Ve
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.SH "CONFORMING TO"
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.IX Header "CONFORMING TO"
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\&\s-1ANSI\s0 X9.62, \s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186\-2
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(Digital Signature Standard, \s-1DSS\s0)
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fIdsa\fR\|(3), \fIrsa\fR\|(3)
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.SH "HISTORY"
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.IX Header "HISTORY"
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The ecdsa implementation was first introduced in OpenSSL 0.9.8
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.SH "AUTHOR"
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.IX Header "AUTHOR"
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Nils Larsch for the OpenSSL project (http://www.openssl.org).
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