This present volume is the Proceedings of the 18th International C- ference on Nearrings and Near?elds held in Hamburg at the Universit] at derBundeswehrHamburgfromJuly27toAugust03,2003. ThisConf- ence was organized by Momme Johs Thomsen and Gerhard Saad from the Universit] at der Bundeswehr Hamburg and by Alexander Kreuzer, Hubert Kiechle and Wen-Ling Huang from the Universit] a ]t Hamburg. It was already the second Conference on Nearrings and Near?elds in Hamburg after the Conference on Nearrings and Near?elds at the same venue from July 30 to August 06, 1995. TheConferencewasattendedby57mathematiciansandmanyacc- panying persons who represented 16 countries from all ?ve continents. The ?rst of these conferences took place 35 years earlier in 1968 at the Mathematische Forschungsinstitut Oberwolfach in the Black Forest inGermany. Thiswasalsothesiteofthesecond, third, ?fthandeleventh conference in 1972, 1976, 1980 and 1989. The other twelve conferences held before the second Hamburg Conference took place in nine di?erent countries. For details about this and, moreover, for a general histo- cal overview of the development of the subject we refer to the article "On the beginnings and developments of near-ring theory" by Gerhard Betsch 3] in the proceedings of the 13th Conference in Fredericton, New Brunswick, Canada. Duringthelast?ftyyearsthetheoryofnearringsandrelatedalgebraic structures like near?elds, nearmodules, nearalgebras and seminearrings has developed into an extensive branch of algebra with its own features."

This present volume is the Proceedings of the 18th International C- ference on Nearrings and Near?elds held in Hamburg at the Universit] at derBundeswehrHamburgfromJuly27toAugust03,2003. ThisConf- ence was organized by Momme Johs Thomsen and Gerhard Saad from the Universit] at der Bundeswehr Hamburg and by Alexander Kreuzer, Hubert Kiechle and Wen-Ling Huang from the Universit] a ]t Hamburg. It was already the second Conference on Nearrings and Near?elds in Hamburg after the Conference on Nearrings and Near?elds at the same venue from July 30 to August 06, 1995. TheConferencewasattendedby57mathematiciansandmanyacc- panying persons who represented 16 countries from all ?ve continents. The ?rst of these conferences took place 35 years earlier in 1968 at the Mathematische Forschungsinstitut Oberwolfach in the Black Forest inGermany. Thiswasalsothesiteofthesecond, third, ?fthandeleventh conference in 1972, 1976, 1980 and 1989. The other twelve conferences held before the second Hamburg Conference took place in nine di?erent countries. For details about this and, moreover, for a general histo- cal overview of the development of the subject we refer to the article "On the beginnings and developments of near-ring theory" by Gerhard Betsch 3] in the proceedings of the 13th Conference in Fredericton, New Brunswick, Canada. Duringthelast?ftyyearsthetheoryofnearringsandrelatedalgebraic structures like near?elds, nearmodules, nearalgebras and seminearrings has developed into an extensive branch of algebra with its own features."

The book contains the first systematic exposition of the current known theory of K-loops, as well as some new material. In particular, big classes of examples are constructed. The theory for sharply 2-transitive groups is generalized to the theory of Frobenius groups with many involutions. A detailed discussion of the relativistic velocity addition based on the author's construction of K-loops from classical groups is also included. The first chapters of the book can be used as a text, the later chapters are research notes, and only partially suitable for the classroom. The style is concise, but complete proofs are given. The prerequisites are a basic knowledge of algebra such as groups, fields, and vector spaces with forms.

Die Kryptologie ist ein aktuelles und attraktives Gebiet. Fur Mathematik- und Informatikstudenten stellt sie eine haufig nachgefragte und angebotene Wahlpflichtveranstaltung dar, die mogliche zukunftige Berufsfelder der Studenten behandelt.
Dieses Lehrbuch bietet einen fundierten Uberblick uber manche klassische hin zu modernen bis zu brandaktuellen kryptografischen Verfahren. Die Voraussetzungen, die ein Leser mitbringen sollte, konzentrieren sich auf wenige Inhalte der linearen Algebra und Analysis, die im ersten Studienjahr vermittelt werden.
Das Buch umfasst im Wesentlichen einen Themenkreis, der in einer vierstundigen Vorlesung angesprochen werden kann. Es zeichnet sich durch mathematische Prazision, zahlreiche Beispiele und viele Algorithmen aus. Bei den Algorithmen wird eine verstandliche Darstellung bevorzugt, die die Prinzipien klar und leicht nachvollziehbar macht. Wegen der ausfuhrlichen Erklarungen kann das Buch auch zum Selbststudium empfohlen werden. Die Kapitel sind in kleine Lerneinheiten unterteilt. Die Leser werden so Schritt fur Schritt von den Anfangen der Kryptologie in der Antike hin zu modernen Verfahren im Internetzeitalter gefuhrt."