One other point with regard to Daniel Nagy's paper at http://www.epointsystem.org/~nagydani/ICETE2005.pdf A good way to organize papers like this is to first present the desired properties of systems like yours (and optionally show that other systems fail to meet one or more of these properties); then to present your system; and finally to go back through and show how your system meets each of the properties, perhaps better than any others. This paper is lacking that last step. It would be helpful to see the epoint system evaluated with regard to each of the listed properties. In particular I have concerns about the finality and irreversibility of payments, given that the issuer keeps track of each token as it progresses through the system. Whenever one token is exchanged for a new one, the issuer records and publishes the linkage between the new token and the old one. This public record is what lets people know that the issuer is not forging tokens at will, but it does let the issuer, and possibly others, track payments as they flow through the system. This could be grounds for reversibility in some cases, although the details depend on how the system is implemented. It would be good to see a critical analysis of how epoints would maintain irreversibility, as part of the paper. CP