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 encr...

Logic access control enforces who can read and write data; the enforcement is typically performed by a fully trusted entity. At TCC 2016, Damgård et al. proposed Access Control Encryption (ACE) schemes where predicate function decides whether or not users (decrypt) (encrypt) data, while message secrecy users’ anonymity are preserved against malicious parties. Subsequently, several ACE construct...