valid certificate

"valid certificate" means a certificate which- (a) a licensed certification authority has issued; (b) has been accepted by the subscriber listed in it; (c) has not been revoked or suspended; and (d) has not expired: Provided that a transactional certificate is a valid certificate only in relation to the digital signature incorporated in it by reference;
ACT 562 - DIGITAL SIGNATURE ACT 1997
2. Interpretation.