@deftypefun {int} {gnutls_pubkey_set_key_usage} (gnutls_pubkey_t @var{key}, unsigned int @var{usage})
@var{key}: a certificate of type @code{gnutls_x509_crt_t} 

@var{usage}: an ORed sequence of the GNUTLS_KEY_* elements.

This function will set the key usage flags of the public key. This
is only useful if the key is to be exported to a certificate or
certificate request.

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

@strong{Since:} 2.12.0
@end deftypefun