Explaining cryptographic systems TimBell a, *, Harold Thimbleby b ,MikeFellows c ,IanWitten d ,NeilKoblitz e , Matthew Powell a a University of Canterbury, Christchurch, New Zealand b University College London, London, UK c University of Newcastle, Australia d University of Waikato, Hamilton, New Zealand e University of Washington, Seattle, USA Received 12 December 2000; accepted 29 July 2002 Abstract Modern cryptography can achieve levels of security and authentication that non-specialists find literally incredible. Techniques including information-hiding protocols, zero-knowledge proofs and public key cryptosystems can be used to support applications like digital signatures, digital cash, on-line poker and securevotinginwaysthatareprovablysecure—farmoresecurethanthetraditionalsystemstheyreplace. This paper describes simple versions of such applications that have been used to give school-children and the general public a broad understanding of what can be achieved, and how. The material has been extensivelyandsuccessfullyusedbytheauthorsinschools,sciencefestivalsandwithundergraduates,and even postgraduate specialists. # 2002ElsevierScienceLtd.Allrightsreserved. Keywords: Cryptography; Public understanding of science; Security; Privacy 1. Introduction Security and privacy are pressing social issues in an era when much commerce is conducted electronically, and personal information is stored on computers and transmitted over computer networks. Modern cryptographic systems can implement extremely high levels of security, but theircapabilitiesarenotwidelyappreciatedbythegeneralpublic.Forexample,manypeopleuse debitcardstopayforgoods,wheremoneyistransferreddirectlyfromtheirbankaccounttothe store’s.Intheprocessthebankfindsoutwherethepurchaseisbeingmade,andcouldbuildupa 0360-1315/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII:S0360-1315(02)00102-1 Computers & Education 40 (2003) 199–215 www.elsevier.com/locate/compedu * Corresponding author. E-mail address: tim.bell@canterbury.ac.nz (T. Bell).