Abstract

An efficient end-to-end encryption system including key management procedures for providing secure, financial data communication between a system user at one of a plurality of transaction terminals of one of a plurality of acquirer institutions and one of a plurality of issuer institutions, with selected elements of the data being encrypted, decrypted, and processed using a onetime session key which is similarly encrypted with master keys and efficiently sent along with the specific segments of the request and response messages. A session key authentication code is utilized to prevent the replay of a previously used session key, thereby precluding undetected message replay or undetected message or data element substitution or insertion.