NetBSD/lib/libcrypto/man/DSA_sign.3

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.TH DSA_sign 3 "0.9.5a" "22/Jul/100" "OpenSSL"
.UC
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.rm #[ #] #H #V #F C
.SH "NAME"
DSA_sign, DSA_sign_setup, DSA_verify \- DSA signatures
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/dsa.h>
.Ve
.Vb 2
\& int DSA_sign(int type, const unsigned char *dgst, int len,
\& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
.Ve
.Vb 2
\& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
\& BIGNUM **rp);
.Ve
.Vb 2
\& int DSA_verify(int type, const unsigned char *dgst, int len,
\& unsigned char *sigbuf, int siglen, DSA *dsa);
.Ve
.SH "DESCRIPTION"
\fIDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
digest \fBdgst\fR using the private key \fBdsa\fR and places its ASN.1 DER
encoding at \fBsigret\fR. The length of the signature is places in
*\fBsiglen\fR. \fBsigret\fR must point to \fIDSA_size\fR\|(\fBdsa\fR) bytes of memory.
.PP
\fIDSA_sign_setup()\fR may be used to precompute part of the signing
operation in case signature generation is time-critical. It expects
\fBdsa\fR to contain DSA parameters. It places the precomputed values
in newly allocated \fBBIGNUM\fRs at *\fBkinvp\fR and *\fBrp\fR, after freeing
the old ones unless *\fBkinvp\fR and *\fBrp\fR are NULL. These values may
be passed to \fIDSA_sign()\fR in \fBdsa->kinv\fR and \fBdsa->r\fR.
\fBctx\fR is a pre-allocated \fBBN_CTX\fR or NULL.
.PP
\fIDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
matches a given message digest \fBdgst\fR of size \fBlen\fR.
\fBdsa\fR is the signer's public key.
.PP
The \fBtype\fR parameter is ignored.
.PP
The PRNG must be seeded before \fIDSA_sign()\fR (or \fIDSA_sign_setup()\fR)
is called.
.SH "RETURN VALUES"
\fIDSA_sign()\fR and \fIDSA_sign_setup()\fR return 1 on success, 0 on error.
\fIDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
signature and \-1 on error. The error codes can be obtained by
the \fIERR_get_error(3)|ERR_get_error(3)\fR manpage.
.SH "CONFORMING TO"
US Federal Information Processing Standard FIPS 186 (Digital Signature
Standard, DSS), ANSI X9.30
.SH "SEE ALSO"
the \fIdsa(3)|dsa(3)\fR manpage, the \fIerr(3)|err(3)\fR manpage, the \fIrand(3)|rand(3)\fR manpage,
the \fIDSA_do_sign(3)|DSA_do_sign(3)\fR manpage
.SH "HISTORY"
\fIDSA_sign()\fR and \fIDSA_verify()\fR are available in all versions of SSLeay.
\fIDSA_sign_setup()\fR was added in SSLeay 0.8.
.rn }` ''
.IX Title "DSA_sign 3"
.IX Name "DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures"
.IX Header "NAME"
.IX Header "SYNOPSIS"
.IX Header "DESCRIPTION"
.IX Header "RETURN VALUES"
.IX Header "CONFORMING TO"
.IX Header "SEE ALSO"
.IX Header "HISTORY"