Abstract

Attribute-Based Encryption (ABE) is a cryptosystem which supplies access control for an encrypted data in a cloud storage and has been actively studied. However, in the ABE system, a receiver needs much time to decrypt an encrypted data. It is because the cost of pairing operations for decryption becomes heavy linearly with the size of an access structure specified for ciphertexts. Due to this, the construction of ABE is required to reduce the number of pairing operations and achieve expressiveness of an access structure simultaneously. In this paper, we propose a new construction of ciphertext-policy ABE supporting general predicates with a constant number of pairing operations for decryption. We also prove that our construction achieves new security notion which we introduce, restricted-selectively payload-hiding security under the q-type decisional bilinear Deiffie- Hellman assumption.