gnutls_prf(3)                      gnutls                      gnutls_prf(3)

NAME         top

       gnutls_prf - API function

SYNOPSIS         top

       #include <gnutls/gnutls.h>

       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);

ARGUMENTS         top

       gnutls_session_t session
                   is a gnutls_session_t type.

       size_t label_size
                   length of the  label variable.

       const char * label
                   label used in PRF computation, typically a short string.

       int server_random_first
                   non-zero if server random field should be first in seed

       size_t extra_size
                   length of the  extra variable.

       const char * extra
                   optional extra data to seed the PRF with.

       size_t outsize
                   size of pre-allocated output buffer to hold the output.

       char * out  pre-allocated buffer to hold the generated data.

DESCRIPTION         top

       Applies the TLS Pseudo-Random-Function (PRF) on the master secret and
       the provided data, seeded with the client and server random fields.
       For the key expansion specified in RFC5705 see gnutls_prf_rfc5705().

       The  label variable usually contains a string denoting the purpose
       for the generated data.  The  server_random_first indicates whether
       the client random field or the server random field should be first in
       the seed.  Non-zero indicates that the server random field is first,
       0 that the client random field is first.

       The  extra variable can be used to add more data to the seed, after
       the random variables.  It can be used to 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  out , which must be pre-allocated.

NOTE         top

       This function produces identical output with gnutls_prf_rfc5705()
       when  server_random_first is set to 0 and  extra is NULL.

RETURNS         top

       GNUTLS_E_SUCCESS on success, or an error code.

REPORTING BUGS         top

       Report bugs to <>.
       Home page:

COPYRIGHT         top

       Copyright © 2001-2017 Free Software Foundation, Inc., and others.
       Copying and distribution of this file, with or without modification,
       are permitted in any medium without royalty provided the copyright
       notice and this notice are preserved.

SEE ALSO         top

       The full documentation for gnutls is maintained as a Texinfo manual.
       If the /usr/share/doc/gnutls/ directory does not contain the HTML
       form visit 

COLOPHON         top

       This page is part of the GnuTLS (GnuTLS Transport Layer Security
       Library) project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       tarball gnutls-3.6.1.tar.xz fetched from
       ⟨⟩ on 2018-02-02.  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail

gnutls                              3.6.1                      gnutls_prf(3)