Fair mobile payment protocols ensure that both participants can engage in the exchange without the risk of suffering a disadvantage (e.g., losing their money without receiving anything for it). In general, fair payment protocols require the continuous availability of an external trusted third party(TTP), a dedicated site which is trusted by both participants. In this paper we present solutions to the fair exchange problem in mobile environments, where customers frequently disconnect from the network and thus continuous availability of the external TTP is not given. Our approach utilizes smart card on the customer?s side partly taking over the duties of the TTP. A novel digital cash protocol is also proposed. In the protocol we implement a distributed anonymity provider agent with smart card on the customer?s side. Thus accountable anonymity is guaranteed. Compared with Chaum?s and Wang?s schemes its communication cost and customer?s computation are more reduced. The proposed digital cash are proved to be unreusable, unexpandable, untraceable, and unforgeable.