A Provably Secure Parallel Certificatelesss Ring Signcryption Scheme

摘要

Ring signcryption is a cryptographic primitivewhich combines the functions of a ring signature scheme andan encryption scheme. It can provide confidentiality, anonymityand authenticity simultaneously. In this paper, we show asecurity flaw in a previous certificateless ring signcryptionscheme (Wang et al.ȁ9;s scheme) and propose an efficient parallelring signcryption scheme in certificateless public key setting.Compared with Wang et al.ȁ9;s scheme, our new scheme needs 3less pairings and enjoys a shorter ciphertext. Furthermore theparallel execution of the expensive signature and encryptionoperations in our scheme implies a gain in running efficiency.We also prove that the new scheme is not only indistinguishableagainst chosen-ciphertext attacks but also existentially unforgeableagainst chosen-message attacks.