2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/154256We study the problem of preventing double spending in electronic payment schemes in a distributed fashion. This problem occurs, for instance, when the spending of electronic coins needs to be controlled by a large collection of nodes (eg. in a peer-to-peer (P2P) system) instead of one central bank. Contrary to the commonly held belief that this is fundamentally impossible, we propose several solutions that do achieve a reasonable level of double spending prevention, and analyse their efficiency under varying assumptions.15th Int. Workshop on Security Protocols, 2007 (to appear)Cryptography and Securitytext