gnutls\_hkdf\_extract(3) gnutls gnutls\_hkdf\_extract(3)

# [NAME](#NAME)

gnutls\_hkdf\_extract - API function

# [SYNOPSIS](#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](#ARGUMENTS)

[gnutls\_mac\_algorithm\_t mac](#gnutls_mac_algorithm_t)

the mac algorithm used internally

[const gnutls\_datum\_t * key](#const)

the initial keying material

[const gnutls\_datum\_t * salt](#const~2)

the optional salt

[void * output](#void)

the output value of the extract operation

# [DESCRIPTION](#DESCRIPTION)

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

# [RETURNS](#RETURNS)

Zero or a negative error code on error.

# [SINCE](#SINCE)

3.6.13

# [REPORTING BUGS](#REPORTING_BUGS)

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

# [COPYRIGHT](#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](#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/](https://www.gnutls.org/manual/)

3.8.13 gnutls

---

Document: gnutls_hkdf_extract(3) from gnutls 3.8.13-r1 (Chainguard OS)
Source: https://gitlab.com/gnutls/gnutls