When systems for electronic commerce are devised, or when existing solutions are selected, the following attributes must be present:- Authentication - are parties to the transaction who they claim to be? This is achieved through the us.e of digital certificates - Privacy and confidentiality - are transaction data protected? The consumer may want to make an anonymous purchase. Are all non-essential traces of a transaction removed from the public network and all intermediary records eliminated? - Integrity - checks that the message sent is complete, i.e. that is not corrupted. - Non-repudiability - ensures sender cannot deny sending message. - Availability - how can threats to the continuity and performance of the system be eliminated?