Short-ciphertext and BDH-based CCA2 secure certificateless encryption

Abstract

Certificateless public key cryptosystem actually belongs to identity based cryptography, with an attractive characteristic that the private key generator does not have access to any user’s full private key. Most of the existing certificateless encryption schemes employ the FO-technique and/or strong assumptions, for example GBDH, Gap-BDH and BDHI, to achieve adaptive chosen ciphertext security (CCA2 security). However, FO-technique introduces redundancy in ciphertext, and strong assumption reduces our confidence in the security of the underlying scheme. In this paper, we present a short-ciphertext CCA2 secure certificateless encryption scheme under the standard BDH assumption. Due to short ciphertext and convincing security, our scheme has practical value.