PhiAttack

Abstract

Compiling Java Card applets is based on the assumption that export files used to translate Java class item to Java Card CAP tokens are legitimate. Bouffard et al.[2] reversed the translation mechanism. Based on malicious Application Programming Interface (API) embedded in a target, they succeeded in making a man-in-the-middle attack where cryptographic keys can leak. In this article, we disclose that, on a pool of legitimate export files, Java Card Virtual Machine (JCVM) implementations can be confused by a CAP file verified by the Java Card Bytecode Verifier (BCV). The disclosed vulnerability leads to Java Card class hierarchy rewriting. The introduced vulnerability is exploitable up to Java Card 3.0.5. Recently, Java Card 3.1.0 provides a new export file format which prevents this vulnerability.