CCA Secure Threshold KEM Scheme Against Adaptive Corruption Attacks in Standard Model

Abstract

Most threshold key encapsulation mechanisms (KEM) have been studied in a weak model–static corruption model or random oracle model. In this paper, we propose a threshold KEM scheme with provable security based on the bilinear groups of composite order in the standard model. We use a direct construction from Boyen-Mei-Waters’ KEM scheme and Libert and Yung’s threshold decryption scheme to obtain a threshold KEM scheme that can withstand adaptive chosen ciphertext attacks (CCA) and adaptive corruption attacks. However, to achieve a higher security level, our construction does not increase overall additional size of ciphertext compare to other schemes.