.\" DO NOT MODIFY THIS FILE!  It was generated by gdoc.
.TH "gnutls_prf" 3 "2.4.2" "gnutls" "gnutls"
.SH NAME
gnutls_prf \- derive pseudo-random data using the TLS PRF
.SH SYNOPSIS
.B #include <gnutls/gnutls.h>
.sp
.BI "int gnutls_prf(gnutls_session_t " session ", size_t " label_size ", const char * " label ", int " server_random_first ", size_t " extra_size ", const char * " extra ", size_t " outsize ", char * " out ");"
.SH ARGUMENTS
.IP "gnutls_session_t session" 12
is a \fBgnutls_session_t\fP structure.
.IP "size_t label_size" 12
length of the \fIlabel\fP variable.
.IP "const char * label" 12
label used in PRF computation, typically a short string.
.IP "int server_random_first" 12
non-0 if server random field should be first in seed
.IP "size_t extra_size" 12
length of the \fIextra\fP variable.
.IP "const char * extra" 12
optional extra data to seed the PRF with.
.IP "size_t outsize" 12
size of pre-allocated output buffer to hold the output.
.IP "char * out" 12
pre-allocate buffer to hold the generated data.
.SH "DESCRIPTION"
Apply the TLS Pseudo\-Random\-Function (PRF) using the master secret
on some data, seeded with the client and server random fields.

The \fIlabel\fP variable usually contain a string denoting the purpose
for the generated data.  The \fIserver_random_first\fP indicate whether
the client random field or the server random field should be first
in the seed.  Non\-0 indicate that the server random field is first,
0 that the client random field is first.

The \fIextra\fP variable can be used to add more data to the seed, after
the random variables.  It can be used to tie make sure the
generated output is strongly connected to some additional data
(e.g., a string used in user authentication).

The output is placed in *\fIOUT\fP, which must be pre\-allocated.
.SH "RETURNS"
\fBGNUTLS_E_SUCCESS\fP on success, or an error code.
.SH "REPORTING BUGS"
Report bugs to <bug-gnutls@gnu.org>.
.SH COPYRIGHT
Copyright \(co 2008 Free Software Foundation.
.br
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
.SH "SEE ALSO"
The full documentation for
.B gnutls
is maintained as a Texinfo manual.  If the
.B info
and
.B gnutls
programs are properly installed at your site, the command
.IP
.B info gnutls
.PP
should give you access to the complete manual.