An efficient signcryption scheme with key privacy
In Information Processing Letters 2006, Tan pointed out that the anonymous signcryption scheme proposed by Yang, Wong and Deng (YWD) in ISC 2005 provides neither confidentality nor anonymity. However, no discussion has been made on whether YWD scheme can be made secure. In this paper, we propose a modification of YWD scheme which resolves the security issues of the original scheme without sacrificing its high efficiency and simple design. Indeed, we show that our scheme achieves confidentiality, existential unforgeability and anonymity with more precise reduction bounds. In addition, our scheme further improves the efficiency when compared with YWD, with reduced number of operations for both signcryption and de-signcryption.