Dynamic Attribute-Based Encryption Scheme Based on Hierarchical Time Tree

Aiming at the problem of authorization access and authorization revocation caused by user changes in attribute-based encryption. This paper proposes an attribute-based encryption scheme that can authorize new temporary users and effectively revocation temporary user access rights. This scheme first uses proxy re-encryption technology to update the ciphertext access policy, so that new users can be added to the system at any time without rebuilding the system. By introducing the hierarchical time tree, the time validity is added to the decryptable period in the user key and ciphertext. Only temporary users whose attributes meet the access policy and the validity period of attribute key completely covers the decipherable period of re-encrypted ciphertext can be decrypted. Achieve the purpose of expiring temporary user access. The scheme not only improves the scalability of attribute encryption scheme, but also reduces the computational cost of users.