Bounds on authentication systems in query mode

Unconditionally secure authentication codes provide information theoretic security against an adversary who observes authenticated messages and then wants to construct a fraudulent message that is acceptable by the receiver. The attack model for these codes has recently been strengthened and adaptive adversaries with oracle access have been introduced. In this paper we give an analysis of this new model and derive information theoretic bounds on the success probability and key size of the codes. Our analysis treats two games that an adversary can play: an offline attack in which the adversary is allowed to query a verification oracle and then to construct the spoofing query; and an on-line attack in which the adversary interacts with the verification oracle and wins as soon as he constructs an acceptable message. We describe the best strategy of the adversary in each case. Disciplines Physical Sciences and Mathematics Publication Details This article was originally published as: Safavi-Naini, R & Wild, P, Bounds on authentication systems in query mode, IEEE Information Theory Workshop on Theory and Practice in Information-Theoretic Security 2005, 16-19 October 2005, 85-91. Copyright IEEE 2005. This conference paper is available at Research Online: http://ro.uow.edu.au/infopapers/445 Bounds on Authentication Systems in Query Model Reihaneh Safavi-Naini School of Information Technology and Computer Science University of Wollongong Wollongong, Australia Email: [email protected] Peter Wild Department of Mathematics Royal Holloway University of London Egham, Surrey TW20 0EX, UK Email: [email protected] Abstract—Unconditionally secure authentication codes provide information theoretic security against an adversary who observes authenticated messages and then wants to construct a fraudulent message that is acceptable by the receiver. The attack model for these codes has recently been strengthened and adaptive adversaries with oracle access have been introduced. In this paper we give an analysis of this new model and derive information theoretic bounds on the success probability and key size of the codes. Our analysis treats two games that an adversary can play: an offline attack in which the adversary is allowed to query a verification oracle and then to construct the spoofing query; and an on-line attack in which the adversary interacts with the verification oracle and wins as soon as he constructs an acceptable message. We describe the best strategy of the adversary in each case.