X-Cash: Executable Digital Cash

Markus Jakobsson, Ari Juels

Abstract: In this paper, we propose a new financial instrument known as executable digital cash, or X-cash. X-cash is a means of binding an offer to the accompanying goods or payment, enabling the processes of searching and paying to be unified. The result is a mechanism by which electronic trades can occur in a highly distributed setting with strong security guarantees. When a party receives an X-cash offer, he or she can verify that it is bona fide and can initiate a trade immediately, without contacting the originator directly. X-cash may therefore be used, among other things, to enable mobile agents to carry funds and make payments on-site without running the risk of ”pick-pocketing”. In this paper, we introduce X-cash, describe some variants, and sketch proofs of its security properties.