Study on cryptographic protocols

Cryptographic algorithms, when used in networks, are used within a cryptographic protocol. In the ENISA algorithms report of 2013 [113], several protocols were discussed. In this document (which is the sister document of the 2014 report [115]) we extend the work in the 2013 report to cover more categories of protocols. The focus of this report is on decision makers in corporations and governments making decisions as to what protocols to use so as to protect online communications which contain personal data which needs to be kept private. Even if the cryptographic primitives and schemes (discussed in [115]) are deemed secure, their use within a protocol can result in a vulnerability which exposes the supposedly secured data. Another focus of the report is to point out the paucity of work, which demonstrates that standard protocols meet well defined security goals. Thus the report, hopefully, will act as a stimulus to researchers and funders in this area to focus efforts on the important area of cryptographic protocols. Whilst the security of basic cryptographic building blocks, such as primitives and protocols, is well studied and understood, the same cannot be said of cryptographic protocols. The scientific study of such protocols can be said to be still not mature enough. As an example of this infancy we point to the discussion in this document on TLS (Transport Layer Security) security, Section 3.1. The TLS protocol is the protocol used to secure traffic from web-sites to browsers; despite a lot of effort on understanding this protocol in the last few years, basic protocol errors are still being found (e.g. Lucky13 [17]), as well as implementation errors (e.g. HeartBleed [87]). In this report we focus on the former type of problems as opposed to the latter type of problems.