gnutls_prf — API function


#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);


gnutls_session_t session

is a gnutls_session_t structure.

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−0 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.


Applies the TLS Pseudo−Random−Function (PRF) on the master secret and the provided data, seeded with the client and server random fields, as specified in 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−0 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.


GNUTLS_E_SUCCESS on success, or an error code.


Report bugs to <>.

General guidelines for reporting bugs:

GnuTLS home page:


The full documentation for gnutls is maintained as a Texinfo manual. If the info and gnutls programs are properly installed at your site, the command

info gnutls

should give you access to the complete manual. As an alternative you may obtain the manual from:


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