Further improvement of an identity-based signcryption scheme in the standard model

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 2009, Yu et al. proposed an identity-based signcryption scheme in the standard model. In 2010, Jin et al. pointed out that Yu et al.'s scheme cannot achieve the semantic security and proposed an improved identity-based signcryption scheme. They proved that the improved scheme is semantically secure in the standard model. Recently, Li et al. showed that the Jin-et al.'s scheme cannot achieve the semantic security and existential unforgeability. To remedy the weaknesses of the Jin-et al.'s scheme, we give a further improvement in this paper. Our scheme satisfies semantic security and existential unforgeability.