17 (c) the course of dealing between the person relying on the digitally signed electronic record and the subscriber and any available indication of reliability or unreliability other than the digital signature; and (d) any usage of trade, particularly trade conducted by trustworthy systems or other electronic means. PART VII - OBLIGATIONS RELATING TO DIGITAL SIGNATURES 22. Reliance on certificates Any person relying on a digital signature shall also rely on a valid certificate containing the public key by which the digital signature can be verified. 23. Prerequisites to publication of certificates No person shall publish a certificate or otherwise make it available to a person known by that person to be in a position to rely on the certificate or on a digital signature that is verifiable with reference to a public key listed in the certificate, where that person knows that (a) the certification authority referred to in the certificate has not issued it; (b) the subscriber listed in the certificate has not accepted it; or (c) the certificate has been revoked or suspended, unless the publication is for the purpose of verifying a digital signature created prior to such suspension or revocation. PART VIII - OBLIGATIONS OF CERTIFICATION AUTHORITIES 24. Trustworthy system Every certification authority shall utilise a trustworthy system in performing its services. 25. Disclosure (1) A certification authority shall disclose (a) its certificate that contains the public key corresponding to the private key used by that certification authority to digitally