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135 .IX Title "DSA_sign 3"
136 .TH DSA_sign 3 "2016-05-03" "1.0.1t" "OpenSSL"
137 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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142 DSA_sign, DSA_sign_setup, DSA_verify \- DSA signatures
144 .IX Header "SYNOPSIS"
146 \& #include <openssl/dsa.h>
148 \& int DSA_sign(int type, const unsigned char *dgst, int len,
149 \& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
151 \& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
154 \& int DSA_verify(int type, const unsigned char *dgst, int len,
155 \& unsigned char *sigbuf, int siglen, DSA *dsa);
158 .IX Header "DESCRIPTION"
159 \&\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
160 digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN.1 DER\s0
161 encoding at \fBsigret\fR. The length of the signature is places in
162 *\fBsiglen\fR. \fBsigret\fR must point to DSA_size(\fBdsa\fR) bytes of memory.
164 \&\fIDSA_sign_setup()\fR may be used to precompute part of the signing
165 operation in case signature generation is time-critical. It expects
166 \&\fBdsa\fR to contain \s-1DSA\s0 parameters. It places the precomputed values
167 in newly allocated \fB\s-1BIGNUM\s0\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
168 the old ones unless *\fBkinvp\fR and *\fBrp\fR are \s-1NULL.\s0 These values may
169 be passed to \fIDSA_sign()\fR in \fBdsa\->kinv\fR and \fBdsa\->r\fR.
170 \&\fBctx\fR is a pre-allocated \fB\s-1BN_CTX\s0\fR or \s-1NULL.\s0
172 \&\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
173 matches a given message digest \fBdgst\fR of size \fBlen\fR.
174 \&\fBdsa\fR is the signer's public key.
176 The \fBtype\fR parameter is ignored.
178 The \s-1PRNG\s0 must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
181 .IX Header "RETURN VALUES"
182 \&\fIDSA_sign()\fR and \fIDSA_sign_setup()\fR return 1 on success, 0 on error.
183 \&\fIDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
184 signature and \-1 on error. The error codes can be obtained by
185 \&\fIERR_get_error\fR\|(3).
187 .IX Header "CONFORMING TO"
188 \&\s-1US\s0 Federal Information Processing Standard \s-1FIPS 186 \s0(Digital Signature
189 Standard, \s-1DSS\s0), \s-1ANSI X9.30\s0
191 .IX Header "SEE ALSO"
192 \&\fIdsa\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
193 \&\fIDSA_do_sign\fR\|(3)
196 \&\fIDSA_sign()\fR and \fIDSA_verify()\fR are available in all versions of SSLeay.
197 \&\fIDSA_sign_setup()\fR was added in SSLeay 0.8.