gnutls\_hkdf\_expand(3) gnutls gnutls\_hkdf\_expand(3)

# [NAME](#NAME)

gnutls\_hkdf\_expand - API function

# [SYNOPSIS](#SYNOPSIS)

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

**int gnutls\_hkdf\_expand(gnutls\_mac\_algorithm\_t mac, const gnutls\_datum\_t * key, const gnutls\_datum\_t * info, void * output, size\_t length);**

# [ARGUMENTS](#ARGUMENTS)

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

the mac algorithm used internally

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

the pseudorandom key created with HKDF-Extract

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

the optional informational data

[void * output](#void)

the output value of the expand operation

[size\_t length](#size_t)

the desired length of the output key

# [DESCRIPTION](#DESCRIPTION)

This function will derive a variable length keying material from the pseudorandom key using the HKDF-Expand 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

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Document: gnutls_hkdf_expand(3) from gnutls 3.8.13-r3 (Chainguard OS)
Source: https://gitlab.com/gnutls/gnutls