Security Protocols in a Nutshell Mohsen Toorani Department of Informatics University of Bergen, Norway
[email protected] Abstract Security protocols are building blocks in secure communications. They deploy some security mechanisms to provide certain security services. Security protocols are considered abstract when analyzed, but they can have extra vulnerabilities when implemented. This manuscript provides a holistic study on security protocols. It reviews foundations of security protocols, taxonomy of attacks on security protocols and their implementations, and different methods and models for security analysis of protocols. Specifically, it clarifies differences between information-theoretic and computational security, and computational and symbolic models. Furthermore, a survey on computational security models for authenticated key exchange (AKE) and password-authenticated key exchange (PAKE) protocols, as the most impor- tant and well-studied type of security protocols, is provided. Keywords: Cryptographic protocols, Authenticated key exchange, Computational security, Provable security, Security models. arXiv:1605.09771v2 [cs.CR] 2 Jun 2016 Copyright c 2015 Mohsen Toorani. All Rights Reserved. Contents 1 Introduction 1 1.1 Security attacks . 2 1.2 Security services . 2 1.3 Security mechanisms . 3 2 Taxonomy of attacks 3 2.1 Attacks on security protocols . 3 2.2 Attacks on encryption schemes . 8 2.3 Attacks on implementations . 11 3 Security models 14 3.1 Information-theoretic vs computational security . 15 3.2 Idealized models in computational security . 16 3.3 Formal security models . 18 3.4 Security proofs in reality . 19 4 Security models for cryptographic protocols 20 4.1 AKE protocols . 22 4.1.1 Security models for AKE protocols . 23 4.1.2 PAKE protocols .