Computationally Sound Analysis of a Probabilistic Contract Signing Protocol
Abstract. We propose a probabilistic contract signing protocol that achieves balance even in the presence of an adversary that may,delay messages sent over secure channels. To show that this property holds in a computational setting, we rst propose a probabilistic framework for protocol analysis, then prove that in a symbolic setting the proto- col satises,a probabilistic alternating-time temporal formula expressing balance, and nally establish a general result stating that the validity of formulas such as our balance formula is preserved when passing from the symbolic to a computational setting. The key idea of the protocol is to take a \gradual commitment" approach.