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140 .IX Title "DSA_sign 3"
141 .TH DSA_sign 3 "0.9.6e" "2000-04-13" "OpenSSL"
144 DSA_sign, DSA_sign_setup, DSA_verify \- \s-1DSA\s0 signatures
146 .IX Header "SYNOPSIS"
148 \& #include <openssl/dsa.h>
151 \& int DSA_sign(int type, const unsigned char *dgst, int len,
152 \& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
155 \& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
159 \& int DSA_verify(int type, const unsigned char *dgst, int len,
160 \& unsigned char *sigbuf, int siglen, DSA *dsa);
163 .IX Header "DESCRIPTION"
164 \&\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
165 digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN\s0.1 \s-1DER\s0
166 encoding at \fBsigret\fR. The length of the signature is places in
167 *\fBsiglen\fR. \fBsigret\fR must point to DSA_size(\fBdsa\fR) bytes of memory.
169 \&\fIDSA_sign_setup()\fR may be used to precompute part of the signing
170 operation in case signature generation is time-critical. It expects
171 \&\fBdsa\fR to contain \s-1DSA\s0 parameters. It places the precomputed values
172 in newly allocated \fB\s-1BIGNUM\s0\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
173 the old ones unless *\fBkinvp\fR and *\fBrp\fR are \s-1NULL\s0. These values may
174 be passed to \fIDSA_sign()\fR in \fBdsa->kinv\fR and \fBdsa->r\fR.
175 \&\fBctx\fR is a pre-allocated \fB\s-1BN_CTX\s0\fR or \s-1NULL\s0.
177 \&\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
178 matches a given message digest \fBdgst\fR of size \fBlen\fR.
179 \&\fBdsa\fR is the signer's public key.
181 The \fBtype\fR parameter is ignored.
183 The \s-1PRNG\s0 must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
186 .IX Header "RETURN VALUES"
187 \&\fIDSA_sign()\fR and \fIDSA_sign_setup()\fR return 1 on success, 0 on error.
188 \&\fIDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
189 signature and \-1 on error. The error codes can be obtained by
192 .IX Header "CONFORMING TO"
193 \&\s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186 (Digital Signature
194 Standard, \s-1DSS\s0), \s-1ANSI\s0 X9.30
196 .IX Header "SEE ALSO"
197 dsa(3), err(3), rand(3),
201 \&\fIDSA_sign()\fR and \fIDSA_verify()\fR are available in all versions of SSLeay.
202 \&\fIDSA_sign_setup()\fR was added in SSLeay 0.8.