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[dragonfly.git] / secure / lib / libcrypto / man / DSA_sign.3
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138.\" ======================================================================
139.\"
140.IX Title "DSA_sign 3"
141.TH DSA_sign 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144DSA_sign, DSA_sign_setup, DSA_verify \- \s-1DSA\s0 signatures
145.SH "SYNOPSIS"
146.IX Header "SYNOPSIS"
147.Vb 1
148\& #include <openssl/dsa.h>
149.Ve
150.Vb 2
151\& int DSA_sign(int type, const unsigned char *dgst, int len,
152\& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
153.Ve
154.Vb 2
155\& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
156\& BIGNUM **rp);
157.Ve
158.Vb 2
159\& int DSA_verify(int type, const unsigned char *dgst, int len,
160\& unsigned char *sigbuf, int siglen, DSA *dsa);
161.Ve
162.SH "DESCRIPTION"
163.IX Header "DESCRIPTION"
164\&\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
165digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN\s0.1 \s-1DER\s0
166encoding 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.
168.PP
169\&\fIDSA_sign_setup()\fR may be used to precompute part of the signing
170operation in case signature generation is time-critical. It expects
171\&\fBdsa\fR to contain \s-1DSA\s0 parameters. It places the precomputed values
172in newly allocated \fB\s-1BIGNUM\s0\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
173the old ones unless *\fBkinvp\fR and *\fBrp\fR are \s-1NULL\s0. These values may
174be 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.
176.PP
177\&\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
178matches a given message digest \fBdgst\fR of size \fBlen\fR.
179\&\fBdsa\fR is the signer's public key.
180.PP
181The \fBtype\fR parameter is ignored.
182.PP
183The \s-1PRNG\s0 must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
184is called.
185.SH "RETURN VALUES"
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
189signature and \-1 on error. The error codes can be obtained by
190ERR_get_error(3).
191.SH "CONFORMING TO"
192.IX Header "CONFORMING TO"
193\&\s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186 (Digital Signature
194Standard, \s-1DSS\s0), \s-1ANSI\s0 X9.30
195.SH "SEE ALSO"
196.IX Header "SEE ALSO"
197dsa(3), ERR_get_error(3), rand(3),
198DSA_do_sign(3)
199.SH "HISTORY"
200.IX Header "HISTORY"
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.