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131 .IX Title "DSA_sign 3"
132 .TH DSA_sign 3 "2009-07-23" "0.9.8k" "OpenSSL"
134 DSA_sign, DSA_sign_setup, DSA_verify \- DSA signatures
136 .IX Header "SYNOPSIS"
138 \& #include <openssl/dsa.h>
142 \& int DSA_sign(int type, const unsigned char *dgst, int len,
143 \& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
147 \& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
152 \& int DSA_verify(int type, const unsigned char *dgst, int len,
153 \& unsigned char *sigbuf, int siglen, DSA *dsa);
156 .IX Header "DESCRIPTION"
157 \&\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
158 digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN\s0.1 \s-1DER\s0
159 encoding at \fBsigret\fR. The length of the signature is places in
160 *\fBsiglen\fR. \fBsigret\fR must point to DSA_size(\fBdsa\fR) bytes of memory.
162 \&\fIDSA_sign_setup()\fR may be used to precompute part of the signing
163 operation in case signature generation is time\-critical. It expects
164 \&\fBdsa\fR to contain \s-1DSA\s0 parameters. It places the precomputed values
165 in newly allocated \fB\s-1BIGNUM\s0\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
166 the old ones unless *\fBkinvp\fR and *\fBrp\fR are \s-1NULL\s0. These values may
167 be passed to \fIDSA_sign()\fR in \fBdsa\->kinv\fR and \fBdsa\->r\fR.
168 \&\fBctx\fR is a pre-allocated \fB\s-1BN_CTX\s0\fR or \s-1NULL\s0.
170 \&\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
171 matches a given message digest \fBdgst\fR of size \fBlen\fR.
172 \&\fBdsa\fR is the signer's public key.
174 The \fBtype\fR parameter is ignored.
176 The \s-1PRNG\s0 must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
179 .IX Header "RETURN VALUES"
180 \&\fIDSA_sign()\fR and \fIDSA_sign_setup()\fR return 1 on success, 0 on error.
181 \&\fIDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
182 signature and \-1 on error. The error codes can be obtained by
183 \&\fIERR_get_error\fR\|(3).
185 .IX Header "CONFORMING TO"
186 \&\s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186 (Digital Signature
187 Standard, \s-1DSS\s0), \s-1ANSI\s0 X9.30
189 .IX Header "SEE ALSO"
190 \&\fIdsa\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
191 \&\fIDSA_do_sign\fR\|(3)
194 \&\fIDSA_sign()\fR and \fIDSA_verify()\fR are available in all versions of SSLeay.
195 \&\fIDSA_sign_setup()\fR was added in SSLeay 0.8.