gnutls_prf(3) — Linux manual page


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

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

       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

       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

       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

       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. Under
       TLS1.3 this function will only operate when these conditions are
       true, or otherwise return GNUTLS_E_INVALID_REQUEST.

RETURNS         top

       GNUTLS_E_SUCCESS on success, or an error code.

REPORTING BUGS         top

       Report bugs to <>.
       Home page:

COPYRIGHT         top

       Copyright © 2001- 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-3.7.8.tar.xz fetched from
       ⟨⟩ on 2022-12-17.  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 to

gnutls                            3.7.8                    gnutls_prf(3)