Lazy-mode Ciphertext-update Based Approach for CP-ABE Attribute Change

Abstract

Ciphertext-policy attribute-based encryption(CP-ABE) can be used to realize secure data sharing in cloud computing environments.However,user attribute change(attribute revocation and addition) in CP-ABE is a tricky problem.Generally,attribute change is realized via the proxy server’s secondary encryption of ciphertext and key update.However,when enforcing an attribute change,all ciphertexts related to this attribute should be updated.This paper proposes a user attribute change approach based on lazy-mode ciphertext-update.It analyzes the user’s access ability(before attribute revocation or after attribute addition) to the ciphertexts involved in attribute change and determines if these ciphertexts need to be updated,minimizing the scope of the ciphertexts that need to be updated and reducing the number of updates.This approach improves its efficiency by avoiding unnece-ssary ciphertext updates and shortening the ciphertext while preserving the original security features of the CP-ABE.Finally,a small-size test is conducted to verify the correctness of the proposed approach.

Keywords

• ciphertext-policy attribute-based encryption|attribute revocation|attribute addition|ciphertext update|lazy-mode