An attribute-based encryption scheme is a scheme in which each user is identified by a set of attributes, and some function of those attributes is used to determine decryption ability for each ciphertext. But as an extension for identity-based encryption scheme, the attribute-based schemes are also confronted with the key escrow problem. Furthermore, the attributes belonging to a user usually are monitored by different authorities. One approach to simultaneously resolve the two problems is multi-authority attribute-based encryption schemes, in which the secret keys of the users needed be distributed by different authorities. However, this solution comes at the cost of introducing extra infrastructure and communication.#R##N##R##N#This paper gives a new approach, in which different attributes sets of a user are still certified by different authorities, but the secret key corresponding to the attributes is generated by the central authority. In order to resolve key escrow problem, different authorities generate secret value for the user, but the central authority cannot obtain the secret value. We give a general construction for multi-authority attribute-based encryption scheme using a general attribute-based encryption scheme. Finally, we present a concrete attribute-based encryption scheme secure against the malicious authorities.
['Guoyan Zhang']
A general construction for multi-authority attribute-based encryption