Efficient revocable hierarchical identity-based encryption using cryptographic accumulators

Hierarchical identity-based encryption is an important extension from IBE and has found many applications in the network world. Private key revocation is a crucial requirement for any public key system. In this paper, we propose a novel revocation method for the hierarchical identity-based encryption. Existing revocable hierarchical identity-based encryption schemes have several disadvantages: the key update size increases logarithmically with the number of users in the system, the public information of key update received by each user is different and always related to the level of the identity hierarchy and the security proof of the revocable scheme is very complex. In our scheme, cryptographic accumulators are used to compress hierarchical levels and revoked users’ information into constant values. So we achieve almost constant size of private key update which is irrelevant with the user number in the system. Because of the compression of hierarchical information we can use simple dual system encryption techniques to prove our scheme to be fully secure under several common assumptions without resorting to complex nested dual system encryption techniques.