In July 1998, a summer school in cryptology and data security was organized atthecomputersciencedepartmentofAarhusUniversity,Denmark.Thistook place as a part of a series of summer schools organized by the European Edu- tional Forum, an organizationconsisting of the researchcenters TUCS (Finland), IPA(Holland)andBRICS(Denmark,Aarhus).Thelocalorganizingcommittee consisted of Jan Camenisch, Janne Christensen, Ivan Damga? ard (chair), Karen Møller,andLouisSalvail.ThesummerschoolwassupportedbytheEuropean Union. Modern cryptology is an extremely fast growing ?eld and is of fundamental importance in very diverse areas, from theoretical complexity theory to practical electroniccommerceontheInternet.Wethereforesetouttoorganizeaschool that would enable young researchers and students to obtain an overview of some mainareas,coveringboththeoreticalandpracticaltopics.Itisfairtosaythat the school was a success, both in terms of attendance (136 participants from over20countries)andintermsofcontents.Itisapleasuretothankallofthe speakers for their cooperation and the high quality of their presentations. A total of 13 speakers gave talks: Mihir Bellare, University of California, San Diego; Gilles Brassard, University of Montreal; David Chaum, DigiCash; Ronald Cramer, ETH Zur ¨ ich; Ivan Damg? ard, BRICS; Burt Kaliski, RSA Inc.; Lars Knudsen, Bergen University; Peter Landrock, Cryptomathic; Kevin Mc- Curley, IBM Research, Almaden; Torben Pedersen, Cryptomathic; Bart Preneel, Leuven University; Louis Salvail, BRICS; Stefan Wolf, ETH Zur ¨ ich.