Certificateless Hybrid Signcryption

Signcryption is a cryptographic primitive that fulfills both the functions of digital signature and public key encryption simultaneously, at a cost significantly lower than that required by the traditional signature-then-encryption approach. In this paper, we address a question whether it is possible to construct a hybrid signcryption scheme in the certificateless setting. This question seems to have never been addressed in the literature. We answer the question positively in this paper. In particular, we extend the concept of signcryption tag-KEM to the certificateless setting. We show how to construct a certificateless signcryption scheme using certificateless signcryption tag-KEM. We also give an example of certificateless signcryption tag-KEM.