Cryptanalysis of a Pairing-free Certificateless Signcryption scheme

Signcryption is a very useful cryptographic primitive that aims to achieve authentication and confidentiality in an efficient manner. We cryptanalyze the signcryption scheme of Wei and Ma (2019) which is claimed to be secure. Further, we propose a corresponding modification to show how their signcryption scheme can be made more secure in our proposed signcryption scheme. The security analysis is also applicable to other signcryption schemes with similar design.