Broadcast anti-jamming systems Yvo Desmedt a, * , Rei Safavi-Naini b , Huaxiong Wang b , Lynn Batten c , Chris Charnes d , Josef Pieprzyk b a Department of Computer Science, Florida State University, 206 Love Building, Tallahassee, FL 32306, USA b School of IT and CS, University of Wollongong, Wollongong, NSW 2522, Australia c School of Computing and Mathematics, Deakin University, Clayton, Victoria 3168, Australia d Department of Computer Science and Software Engineering, University of Melbourne, Carlton, Victoria 3053, Australia Received 3 March 2000; accepted 4 April 2000 Corresponding Editor: J.B. Thompson Abstract In a traditional anti-jamming system a transmitter who wants to send a signal to a single receiver spreads th power over a wide frequency spectrum with the aim of stopping a jammer from blocking the transmission. In th we consider the case that there are multiple receivers and the transmitter wants to broadcast a message to all such that colluding groups of receivers cannot jam the reception of any other receiver. We propose ecient coding methods that achieve this goal and link this problem to well-known problems in combinatorics. We also link a gen- eralisation of this problem to the Key Distribution Pattern problem studied in combinatorial cryptography. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Anti-jamming; Cover-free family; Perfect hash family; Key distribution pattern 1. Introduction Security and reliability are two required prop- erties of today's data networks. While reliability is concerned with accidental faults, security deals with malicious ones. System availability is an im- portant consideration from both perspectives. The possibility of a malicious shut down of communi- cations is a major concern, as expressed by the US President's Commission on Critical Infrastructure Protection [24]. Traditional anti-jammingsystems[28] use spread spectrum techniques to increase availabili- ty. In these systemsa transmitterwants to broadcast a signal to a single receiver such that the enemy cannot jam the transmission. In the classi- cal communication scenario, a message modulates a carrier frequencyf which is known to the transmitter and receiver and so the receiver can receivethe message. However if f is publicly known, an outsider can send a strong noise signal on the same frequency and hence completely jam the reception. To protect againstjamming,the transmitter and the receiver can keep their shared frequency secret and use new frequencies after Computer Networks 35 (2001) 223±236 www.elsevier.com/locate/comnet * Corresponding author. Tel.: +1-850-644-92-98. E-mail addresses: desmedt@cs.fsu.edu (Y. Desmedt), rei@ uow.edu.au (R. Safavi-Naini), huaxiong@uow.edu.au (H. Wang), lmbatten@deakin.edu.au (L. Batten),charnes@ cs.mu.oz.au (C. Charnes), josef@uow.edu.au (J. Pieprzyk). 1389-1286/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 9 - 1 2 8 6 ( 0 0 ) 0 0 1 6 9 - 9