nvented abstract representations of value. As time passed, representations of value became more abstract, progressing from barter through bank notes, payment orders, checks, credit cards, and now electronic payment systems. Traditional means of payment suffer from various well-known security problems: Money can be counterfeited, signatures forged, and checks bounced. Electronic means of payment retain the same drawbacks and some additional risks: Unlike paper, digital "documents" can be copied perfectly and arbitrarily often; digital signatures can be produced by anybody who knows the secret cryptographic key; a buyer's name can be associated with every payment, eliminating the anonymity of cash. Thus without new security measures, widespread electronic commerce is not viable. On the other hand, properly designed electronic payment systems can actually provide better security than traditional means of payments, in addition to flexibility of use. This article provides an ...
N. Asokan, Philippe A. Janson, Michael Steiner, Mi