Ciphertext-policy attribute-based encryption（CP-ABE）allows a user with some attributes to decrypt the ciphertexts associated with these attributes.Though several CP-ABE schemes with the constant size ciphertext were proposed to reduce the communication cost,their master public and secret keys still have the size linear in the total number of attributes.These schemes are unpractical for the attribute-scalable and many-attributes scenario.A new CP-ABE scheme is proposed.Each attribute is mapped to a mathematical value by a combination method.The master public and secret keys of the proposed CP-ABE scheme have the size linear in the binary size of a hash function’s range.It has the comparable performance with existing schemes in the aspects like the time costs of encryption and decryption,the expressiveness of access policy and the provable security.
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