Generic Construction of Bounded-Collusion IBE via Table-Based ID-to-Key Map

In this paper, we give a new generic construction of bounded-collusion identity-based encryption (BC-IBE) scheme from public key encryption (PKE) scheme. Our construction significantly reduces the number of public parameters to O(t), where t is a collusion parameter. Especially, we present the first construction in which the number of public parameters is independent from the total number of identities in the system. To achieve this, we propose a novel table-based ID-to-key map, and a method of deriving key pair from two (public and secret) parameter tables by using a cryptographic hash function. We provide a security proof of our construction in random oracle model.