Cryptanalysis of A Pairing-Free Certificateless Signcryption Scheme

Certificateless signcryption (CLSC) has attracted much attention from the research community since it provides both confidentiality and unforgeability, and, at the same time, it does not suffer from the certificate management problem in traditional public key cryptography and the key escrow problem in identity-based cryptography. However, most CLSC schemes are based on the bilinear pairing which is still a time-costing operation although many efforts have been made to improve its efficiency. Recently, Yu et al. proposed a pairing-free CLSC scheme and proved its security. In this paper, we point out that their scheme can be totally broken since confidentiality and unforgeability actually are not captured.