---
name: "gnutls_prf_raw"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_prf_raw"
---

# gnutls\_prf\_raw(3)

API function

## NAME

gnutls\_prf\_raw - API function

## SYNOPSIS

**#include \<gnutls/gnutls.h\>**

**int gnutls\_prf\_raw(gnutls\_session\_t** *session***, size\_t** *label\_size***, const char \*** *label***, size\_t** *seed\_size***, const char \*** *seed***, size\_t** *outsize***, char \*** *out***);**

## ARGUMENTS

- 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.

- size\_t seed\_size

  length of the  *seed* variable.

- const char \* seed

  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

Apply the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data.

The  *label* variable usually contains a string denoting the purpose for the generated data.  The  *seed* usually contains data such as the client and server random, perhaps together with some additional data that is added to guarantee uniqueness of the output for a particular purpose.

Because the output is not guaranteed to be unique for a particular session unless  *seed* includes the client random and server random fields (the PRF would output the same data on another connection resumed from the first one), it is not recommended to use this function directly.  The **gnutls\_prf()** function seeds the PRF with the client and server random fields directly, and is recommended if you want to generate pseudo random data unique for each session.

## NOTE

This function will only operate under TLS versions prior to 1.3. In TLS1.3 the use of PRF is replaced with HKDF and the generic exporters like **gnutls\_prf\_rfc5705()** should be used instead. Under TLS1.3 this function returns **GNUTLS\_E\_INVALID\_REQUEST**.

## RETURNS

**GNUTLS\_E\_SUCCESS** on success, or an error code.

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 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

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

- https://www.gnutls.org/manual/