---
name: "gnutls_x509_crt_get_subject_key_id"
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_x509_crt_get_subject_key_id"
---

# gnutls\_x509\_crt\_get\_subject\_key\_id(3)

API function

## NAME

gnutls\_x509\_crt\_get\_subject\_key\_id - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**int gnutls\_x509\_crt\_get\_subject\_key\_id(gnutls\_x509\_crt\_t** *cert***, void \*** *ret***, size\_t \*** *ret\_size***, unsigned int \*** *critical***);**

## ARGUMENTS

- gnutls\_x509\_crt\_t cert

  should contain a **gnutls\_x509\_crt\_t** type

- void \* ret

  The place where the identifier will be copied

- size\_t \* ret\_size

  Holds the size of the result field.

- unsigned int \* critical

  will be non-zero if the extension is marked as critical (may be null)

## DESCRIPTION

This function will return the X.509v3 certificate's subject key identifier.  This is obtained by the X.509 Subject Key identifier extension field (2.5.29.14).

## RETURNS

On success, **GNUTLS\_E\_SUCCESS** (0) is returned, **GNUTLS\_E\_REQUESTED\_DATA\_NOT\_AVAILABLE** if the extension is not present, otherwise a negative error value.

## 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/