Type-based Analysis of Financial APIs

We examine some known attacks on the PIN verification framework, based on weaknesses of the underlying security API for the tamper-resistant Hardware Security Modules used in the network. We specify this API in an imperative language with cryptographic primitives, and we show how its flaws are captured by a notion of robustness that extends the one of Myers, Sabelfeld and Zdancewic to our cryptographic setting. We propose an improved API, give an extended type system for assuring integrity and for preserving confidentiality via randomized and non-randomized encryptions, and show our new API to be type-checkable.