---
name: "gnutls_hkdf_extract"
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_hkdf_extract"
---

# gnutls\_hkdf\_extract(3)

API function

## NAME

gnutls\_hkdf\_extract - API function

## SYNOPSIS

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

**int gnutls\_hkdf\_extract(gnutls\_mac\_algorithm\_t** *mac***, const gnutls\_datum\_t \*** *key***, const gnutls\_datum\_t \*** *salt***, void \*** *output***);**

## ARGUMENTS

- gnutls\_mac\_algorithm\_t mac

  the mac algorithm used internally

- const gnutls\_datum\_t \* key

  the initial keying material

- const gnutls\_datum\_t \* salt

  the optional salt

- void \* output

  the output value of the extract operation

## DESCRIPTION

This function will derive a fixed-size key using the HKDF-Extract function as defined in RFC 5869.

## RETURNS

Zero or a negative error code on error.

## SINCE

3\.6.13

## 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/