Modelling and Verification of Cash Withdrawal Transaction in Automated Teller Machine Using Timed Automata

This study was conducted to verify a system of Automated Teller Machine (ATM) which is a facility provided by a bank. Various transactions can be done by using ATM, including cash withdrawal, payment, and transfer. However, in spite of its function, ATM can also be a target of crime such as cash robbery and frauds. Therefore, the correctness of ATM and its security is essential and for that reason, formal verification is needed. Formal verification is a technique to ensure the model of a system to satisfy a certain specification. ATM has a time variable on its system. Therefore, timed automata can be used as a model of ATM. In this paper, an algorithm is constructed based on the ATM cash withdrawal steps. Next, we construct a timed automaton model and design nine specifications. Then, timed automaton were verified against these nine specifications using UPPAAL. From the verification results, it can be concluded that the security of the ATM system is guaranteed.