Cryptanalysis of a Certificateless Signcryption Scheme

In 2016, Zheng and Li proposed a certificateless signcryption (CL-SC) scheme and claimed that their scheme is confidential (IND-CCA) and unforgeable (EUF-CMA) against both key replacement and malicious KGC attacks, in the standard model. In this paper, we propose both key replacement and malicious KGC attacks against confidentiality and unforgeability of their scheme. Our proposed attacks show that in contrast to Zheng and Li's claim, their scheme is neither confidential (IND-CCA) nor unforgeable (EUF-CMA) against key replacement and malicious KGC attacks.