Instantaneous Proxy-Based Key Update for CP-ABE

Attribute Based Encryption (ABE) scheme has been proposed to implement cryptographic fine grained access control to shared information. It allows to share information of type one-to-many users, without considering the number of users and their identities. However, original ABE systems suffer from the non-efficiency of their attribute revocation mechanisms. Based on Ciphertext-Policy ABE (CP-ABE) scheme, we propose an efficient proxy-based immediate private key update which does require neither re-encrypting ciphertexts, nor affect other users' secret keys. The semi-trusted proxy assists nodes during the decryption process without having ability to decrypt users' data. Finally, we analyze the security of our scheme and demonstrate that the proposed solution outperforms existing ones in terms of generated overheard.