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134 .IX Title "DSA_sign 3"
135 .TH DSA_sign 3 "2009-11-06" "0.9.8l" "OpenSSL"
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141 DSA_sign, DSA_sign_setup, DSA_verify \- DSA signatures
143 .IX Header "SYNOPSIS"
145 \& #include <openssl/dsa.h>
147 \& int DSA_sign(int type, const unsigned char *dgst, int len,
148 \& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
150 \& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
153 \& int DSA_verify(int type, const unsigned char *dgst, int len,
154 \& unsigned char *sigbuf, int siglen, DSA *dsa);
157 .IX Header "DESCRIPTION"
158 \&\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
159 digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN\s0.1 \s-1DER\s0
160 encoding at \fBsigret\fR. The length of the signature is places in
161 *\fBsiglen\fR. \fBsigret\fR must point to DSA_size(\fBdsa\fR) bytes of memory.
163 \&\fIDSA_sign_setup()\fR may be used to precompute part of the signing
164 operation in case signature generation is time-critical. It expects
165 \&\fBdsa\fR to contain \s-1DSA\s0 parameters. It places the precomputed values
166 in newly allocated \fB\s-1BIGNUM\s0\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
167 the old ones unless *\fBkinvp\fR and *\fBrp\fR are \s-1NULL\s0. These values may
168 be passed to \fIDSA_sign()\fR in \fBdsa\->kinv\fR and \fBdsa\->r\fR.
169 \&\fBctx\fR is a pre-allocated \fB\s-1BN_CTX\s0\fR or \s-1NULL\s0.
171 \&\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
172 matches a given message digest \fBdgst\fR of size \fBlen\fR.
173 \&\fBdsa\fR is the signer's public key.
175 The \fBtype\fR parameter is ignored.
177 The \s-1PRNG\s0 must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
180 .IX Header "RETURN VALUES"
181 \&\fIDSA_sign()\fR and \fIDSA_sign_setup()\fR return 1 on success, 0 on error.
182 \&\fIDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
183 signature and \-1 on error. The error codes can be obtained by
184 \&\fIERR_get_error\fR\|(3).
186 .IX Header "CONFORMING TO"
187 \&\s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186 (Digital Signature
188 Standard, \s-1DSS\s0), \s-1ANSI\s0 X9.30
190 .IX Header "SEE ALSO"
191 \&\fIdsa\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
192 \&\fIDSA_do_sign\fR\|(3)
195 \&\fIDSA_sign()\fR and \fIDSA_verify()\fR are available in all versions of SSLeay.
196 \&\fIDSA_sign_setup()\fR was added in SSLeay 0.8.