Signing Contracts and Paying Electronically

Abstract

Motivated by the increasing use of cryptography, in particular digital signatures, to secure electronic commerce this paper discusses applications of digital signatures. The aim is to give an overview of some problems, which on one hand are related to electronic commerce and, on the other hand, are challenging from a cryptographic point of view. The paper first deals with fundamental techniques for establishing a public key infrastructure and for creating non-repudiation tokens. The latter makes it possible to use digital signatures to serve disputes which is often the ultimate goal when using digital signatures in practice. Next more advanced cryptographic protocols are discussed by giving an overview of protocols for fair exchange of signed documents as well as for implementing electronic cash (prepaid payment systems).