Chapter 13: Limiting Liability in Electronic Commerce

Abstract

Digital signatures are supposed to ensure non-repudiation. However, depending on the environment, attacks might obtain signatures in an underhanded way. This implies conflicting interests: The key holder does not want to be held liable for signatures he has not made. The relying party wants to rely on a digital signature and be able to enforce it in a law court. This chapter tries to find an acceptable compromise. It introduces the necessity for limiting liability for digitally signed transactions, presents the Commitment Service and shows how it can be used as Liability-Cover Service to limit the key holder’s overall liability for digitally signed messages. The main principle is a separation between deniable signatures and undeniable commitments.