An Atomicity-Generating Layer for Anonymous Currencies

Atomicity is a necessary element for reliable transactions (Financial Service Technology Consortium, 1995; Camp, Sirbu and Tygar, 1995; Tygar, 1996). Anonymity is also an issue of great importance not only to designers of commerce systems, (Chaum, 1982; Chaum, 1989; Chaum, Fiat & Naor, 1988; Medvinski, 1993), but also to those concerned with the societal effects of information technologies (Branscomb 1994. Compaine 1985, National Research Council 1996, Neumann 1993, Poole 1983). Yet there has been a tradeoff between these two elements in commerce system design. Reliable systems, which provide highly atomic transactions, offer limited anonymity (Visa, 1995; Sirbu and Tygar, 1995; Mastercard, 1995, Low, Maxemchuk and Paul, 1993) . Anonymous systems (Chaum, 1985; Chaum 1989; Medvinski, 1993) do not offer reliable transactions as shown in Yee, 1994; Camp, 1999; and Tygar, 1996. This work illustrates that any electronic token currency can be made reliable with the addition of this atomicity-generating layer.IB

Is electronic cash possible?

Cash-like payments in electronic commerce and at the traditional point of sale are expected to be beneficial, e.g., because of privacy protection, low transaction costs, and irrevocability. Therefore, we discuss how to design electronic cash in a way that it both mirrors the most important characteristics of raditional cash, but also fulfils the expectations which arise towards electronic means of payment. We analyse the problems and trade-offs between the different characteristics to be implemented. This analysis is based on a user survey and a review of existing technologies for electronic payment systems. Finally we argue why existing systems do not fulfil the critical requirements, and point out future work towards electronic cash which will meet more requirements

The ESPRIT project CAFE - High security digital payment systems

status: publishe

The ESPRIT Project CAFE - High Security Digital Payment Systems

. CAFE ("Conditional Access for Europe") is an ongoing project in the European Community's ESPRIT program. The goal of CAFE is to develop innovative systems for conditional access, and in particular, digital payment systems. An important aspect of CAFE is high security of all parties concerned, with the least possible requirements that they are forced to trust other parties (so-called multi-party security). This should give legal certainty to everybody at all times. Moreover, both the electronic money issuer and the individual users are less dependent on the tamper-resistance of devices than in usual digital payment systems. Since CAFE aims at the market of small everyday payments that is currently dominated by cash, payments are offline, and privacy is an important issue. The basic devices used in CAFE are so-called electronic wallets, whose outlook is quite similar to pocket calculators or PDAs (Personal Digital Assistant). Particular advantages of the electronic wallets are that PIN..

Protocols de seguretat amb terceres parts

Les solucions proposades en els articles científics sobre els intercanvis electrònics entre dues parts sovint involucren terceres parts (TTPs) per resoldre i simplificar el problema, però els usuaris hi han de dipositar una certa confiança. Ara bé, la confiança no és garantia ferma del compliment dels requisits de seguretat. Per això, molts usuaris són reticents a dipositar confiança en entitats remotes, fet que en dificulta l’ús. Aquí mostram com, a partir d’un determinat protocol de seguretat, podem aconseguir que la TTP involucrada sigui verificable. Construïm un entorn de confiança dins del protocol per mitjà del subministrament d’evidències sobre cada una de les operacions de la TTP (definim i introduïm la verificabilitat on-line de la TTP). Aconseguim això gràcies a la detecció, l’anàlisi i la classificació de cada una de les accions de la TTP. Aportam unes orientacions de disseny que faciliten la introducció de TTPs verificables dins dels protocols

A technical approach to privacy based on mobile agents protected by tamper-resistant hardware

We address the problem of protecting the privacy of individuals in the information society. Our goal is to devise technical means that allow users to actively participate in the management and use of information related to them. The advent of the information society creates serious challenges for the privacy of individuals. Due to the drastically improving communication infrastructure, ever larger amounts of ever more precise information become available. The problem with the free availability of this information is not only the risk that the information can be abused by powerful institutions, but also that this can lead to an unconfined mutual surveillance of individuals, which can have adverse effects on society as a whole. We argue that individuals should be empowered to define for themselves the level of privacy they are comfortable with. This can be achieved by notifying them whenever information on them is created, accessed, or modified and by giving them some control over the use of this information. The notification informs individuals who is using what information on them and allows to detect possible problems with this use. The control allows individuals to resolve most (or at least some) of these problems. Obviously this requires that the individuals can trust the users of information to properly implement these notifications and to offer an effective control. We analyze the concept of trust more closely and distinguish between the optimistic and the pessimistic approach to trust, which can both provide the foundation for the protection of privacy. The former is based on the classical concepts of control and sanctions, while the latter tries to prevent malicious behaviour. We choose to pursue the pessimistic approach and investigate in technical means that can be used for this purpose. A promising technology is the mobile agent paradigm, which is a new approach to structure distributed applications. Its main idea is to move both the code and the state of an object to another principal for remote execution. This indicates that the mobile agent paradigm also embraces the object-oriented programming paradigm, which allows us to encapsulate a data item and to specify an access control policy on it. Since the mobile agent is physically moved to a remote location that is under the control of a different principal, it needs to be protected from this principal who is responsible for its execution. This problem constitutes the major diffculty for using the mobile agent paradigm for privacy protection and is explored in great detail. Based on the discussion in the relevant literature, we decide on an approach that relies on a trusted and tamper-resistant hardware device, which is developed on a conceptual level. The approach is further explored in the context of the mobile agent paradigm, where it allows us to realize more elaborate protection goals that may be desirable for the owner of the mobile agent. These are developed in the form of conducts, which regroup the goal, the requirements, as well as a specification of the necessary collaboration to achieve this goal. Finally, we return to the original problem and describe how the presented technology can be used to improve the protection of privacy. This results in a rather complex framework, in which information on individuals cannot be used freely, but where this use is constrained by the level of privacy desired by the subject of the information. The major problem of this framework is the increased complexity that individuals have to deal with. This problem is addressed with an additional level of indirection that attempts to confine the complexity and to delegate it to trusted experts. We believe that this approach, despite its complexity, is a viable means to address the urgent problems of privacy protection, which do not lend themselves to simple solutions