Two-way authentication system between user's smart card and issuer-specific plug-in application modules in multi-issued transaction device

A transaction terminal for use with diverse credit or other transaction cards is provided with an interface unit for receiving a plurality of modules, wherein each module contains programming information corresponding to transactions that may be carried out with at least one of the diverse identification cards presented to the machine. Accordingly, financial institutions who issue cards can independently arrange and program their own security and transaction routines which are to be carried out with the cards and distribute such routines in a secure manner for use on a common terminal.