CCA Secure Publicly Verifiable Public Key Encryption Without Pairings Nor Random Oracle and Its Applications

hosen ciphertext security (CCA security)hosen ciphertext security (CCA security)C is now a widely accepted necessary security notion for public key encryption. CCA secure public verifiable public key encryption has many applications such as threshold public key encryption and proxy re-encryption etc. Furthermore, these years “random oracle model” has seen risen criticize by many cryptographers. Hence, researchers give great effort to pursue public key public key encryption with publicly verifiability in the standard model. However, all the existing CCA secure publicly verifiable public key encryption in the standard model relies on costly bilinear pairing. In this paper, based on Hanaoka and Kurosawa’s efficient CCA secure public key encryption under Computational Diffle-Hellman assumption proposed in Asiacrypt’08 and the famous Cramer-Shoup encryption scheme, we try to construct a CCA secure public verifiable public key encryption without pairing in the standard model. As a result of its application, we achieve a CCA secure public verifiable threshold public key encryption without pairing in the standard model, a CCA secure unidirectional proxy re-encryption without pairing in the standard model.