@deftypefun {int} {gnutls_x509_crl_get_authority_key_id} (gnutls_x509_crl_t @var{crl}, void * @var{id}, size_t * @var{id_size}, unsigned int * @var{critical})
@var{crl}: should contain a @code{gnutls_x509_crl_t}  type

@var{id}: The place where the identifier will be copied

@var{id_size}: Holds the size of the result field.

@var{critical}: will be non-zero if the extension is marked as critical
(may be null)

This function will return the CRL authority's key identifier.  This
is obtained by the X.509 Authority Key identifier extension field
(2.5.29.35).  Note that this function 
only returns the keyIdentifier field of the extension and
@code{GNUTLS_E_X509_UNSUPPORTED_EXTENSION} , if the extension contains
the name and serial number of the certificate. In that case
@code{gnutls_x509_crl_get_authority_key_gn_serial()}  may be used.

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned, otherwise a
negative error code in case of an error.

@strong{Since:} 2.8.0
@end deftypefun