Cash machines (ATMs) and other critical parts of the electronic payment infrastructure contain tamper-proof hardware security modules (HSMs), which protect highly sensitive data such as the keys used to obtain personal identification numbers (PINs). These HSMs have a restricted API that is designed to prevent malicious intruders from gaining access to the data. However, several attacks have been found on these APIs, as the result of painstaking manual analysis by experts such as Mike Bond and Jolyon Clulow.

At the University of Edinburgh, a project is underway to formalise and mechanise the analysis of these APIs. This talk will present some API attacks, and our efforts to generalise them and capture them formally, using theorem provers, protocol analysis tools, and the PRISM probabilistic model checker.