Directly revocable ciphertext-policy attribute-based encryption from lattices

Attribute-based encryption (ABE) is a promising type of cryptosystem achieving fine-grained access control on encrypted data. Revocable attribute-based encryption (RABE) is an extension of ABE that provides revocation mechanisms when user\u27s attributes change, key exposure, and so on. In this paper, we propose two directly revocable ciphertext-policy attribute-based encryption (DR-ABE) schemes from lattices, which support flexible threshold access policies on multi-valued attributes, achieving user-level and attribute-level user revocation, respectively. Specifically, the revocation list is defined and embedded into the ciphertext by the message sender to revoke a user in the user-level revocable scheme or revoke some attributes of a certain user in the attribute-level revocable scheme. We also discuss how to outsource decryption and reduce the workload for the end user. Our schemes are proved to be secure in the standard model, assuming the hardness of the learning with errors (LWE) problem