We propose an efficient revocable multi-authority large-universe attribute-based encryption
system deployed to cloud storage service, which supports multiple authorities issuing secret
keys for users with attributes from different domains in considering of privacy preserving and
efficiency. In addition, it supports large-universe attributes allowing attributes denoted as any
string in a large universe. Furthermore, it realizes an efficient revocation of attributes with
less computation of key updating and data re-encryption. For this system, we define the …