Hammurabi

This paper proposes using a logic programming language to disentangle X.509 certificate validation policy from mechanism. Expressing validation policies in a logic programming language provides multiple benefits. First, policy and mechanism can be more independently written, augmented, and analyzed compared to the current practice of interweaving them within a C or C++ implementation. Once written, these policies can be easily shared and modified for use in different TLS clients. Further, logic programming allows us to determine when clients differ in their policies and use the power of imputation to automatically generate interesting certificates, e.g., a certificate that will be accepted by one browser but not by another.