The prosperous Internet communication technologies have led to e-commerce in mobile computing and made Web of Things become popular. Electronic payment is the most important part of e-commerce, so many electronic payment schemes have been proposed. However, most of proposed schemes cannot give change. Based on proxy blind signatures, an e-cash payment system is proposed in this paper to solve this problem. This system can not only provide change divisibility through Web of Things, but also provide anonymity, verifiability, unforgeability and double-spending owner track.

Recently, Juang proposed an efficient password authenticated key agreement scheme using smart cards for the multi-server architecture. Juang's scheme was intended to provide mutual authentication and session key agreement. Herein, we show that Juang's scheme is vulnerable to a privileged insider's attack and is not easily reparable. Furthermore, it does not provide forward secrecy and the user eviction mechanism.