Abstract
Attribute-Based Encryption (ABE) must provide an efficient revocation mechanism since a user’s private key can be compromised or expired over time. The existing revocable ABE schemes have the drawbacks of heavy computational costs on key updates and encryption operations, which make the entities for performing these operations a possible bottleneck in practice applications. In this paper, we propose an efficient Ciphertext-Policy Attribute-Based Online/Offline Encryption with user Revocation (R-CP-ABOOE). We integrate the subset difference method with ciphertext-policy ABE to significantly improve key-update efficiency on the side of the trusted party from O(rlog(N/r)) to O(r), where N is the number of users and r is the number of revoked users. To reduce the encryption burden for mobile devices, we use the online/offline technology to shift the majority of encryption work to the offline phase, and then mobile devices only need to execute a few simple computations to create a ciphertext. In addition, we exploit a novel trick to prove its selective security under the q-type assumption. Performance analysis shows that our scheme greatly improves the key-update efficiency for the trusted party and the encryption efficiency for mobile devices.
Highlights
Attribute-based encryption (ABE) is a promising alternative of encryption for achieving fine-grained access control of encrypted data
The notion of ABE is first proposed by Sahai and Waters [1], and Goyal et al [2] formalize two supplementary forms of ABE: ciphertext-policy ABE (CPABE) and key-policy ABE (KP-ABE)
In KP-ABE the roles are swapped: a ciphertext is associated with an access policy and the private key is related to a set of attributes
Summary
Attribute-based encryption (ABE) is a promising alternative of encryption for achieving fine-grained access control of encrypted data. Lee et al [8] proposed an efficiently revocable identity-based encryption using subset difference methods, which has O(r) number of group elements in an update key. Our goal is to integrate the subset difference method [6, 8] with ABE to significantly decrease the key update work, and use the online/offline technique to greatly improve the encryption efficiency for mobile devices. We propose an efficient ciphertext-policy attribute-based online/offline encryption with user revocation. Different from prior works, we integrate the SD method with the online/offline technique in the CPABE system, which may efficiently revoke users, and can significantly improve the key-update efficiency and encryption efficiency.
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