A Taxonomy of Metrics for Cryptographic Systems

Measuring the security of cryptographic systems (algorithms, protocols, software and hardware implementations etc.) is a difficult task. There does not exist one simple and easy to measure value that could be used to evaluate the relative strength of different cryptographic systems. On the other hand, there are more and more use cases where protections granted by cryptographic systems are needed. In some cases, there are certification and classification requirements for the use of cryptosystems that would benefit from good measures. Also new standards are being created for cryptography, usually based on competitions, where the proposals are evaluated based on some criteria. In this paper, we describe a taxonomy of the multiple metrics that can be associated with cryptographic systems and evaluate them based on a number of different attributes. We also reflect our taxonomy to the decisions made in several cryptographic standardisation competitions.