Improved Conditional E-Payments

Conditional e-cash or conditional e-payments have been introduced by Shi et al. as the means for enabling electronic payments to be based on the outcome of a certain condition not known in advance. In this framework, a payer obtains an electronic coin and can transfer it to a payee under a certain condition. Once the outcome of the condition is known, if it was favorable to the payee, the payee can deposit the coin; otherwise, the payer keeps the money. In this work, we formalize conditional payments and give a scheme to achieve conditional e-payments that outperforms the original solution in several respects.