Flexible Attribute-Based Encryption

Abstract

Abstract. In this paper, we propose a notion of flexible attribute-based encryption. Flexible attribute-based encryption is a variant of ciphertextpolicy ABE, which allows one to loosen a decryption policy underlying a given ciphertext, if one knows some system-wide trapdoor information, without knowing its underlying plaintext message. We give a concrete construction of the flexible attribute-based encryption that satisfies indistinguishability under the loosening operation, based on the construction of ciphertext-policy ABE given by Bethencourt, Sahai and Waters.