Modeling Computational Security in Long-Lived Systems

Abstract. For many cryptographic protocols, security relies on the assumption that adversarial entities have limited computational power. This type of security degrades progressively over the lifetime of a protocol. However, some cryptographic services, such as timestamping services or digital archives, are long-lived in nature; they are expected to be secure and operational for a very long time (i.e., super-polynomial). In such cases, security cannot be guaranteed in the traditional sense: a computationally secure protocol may become insecure if the attacker has a super-polynomial number of interactions with the protocol. This paper proposes a new paradigm for the analysis of long-lived security protocols. We allow entities to be active for a potentially unbounded amount of real time, provided they perform only a polynomial amount of work per unit of real time. Moreover, the space used by these entities is allocated dynamically and must be polynomially bounded. We propose a new notion...

• Type: Conference
• Year: 2008
• Where: CONCUR
• Authors: Ran Canetti, Ling Cheung, Dilsun Kirli Kaynar, Nancy A. Lynch, Olivier Pereira
• Keywords: CONCUR 2008, Distributed And Parallel Computing, Long-lived Security Protocols, Long-lived Timestamping Protocol, Security