Circuit Ciphertext-policy Attribute-based Hybrid Encryption with Verifiable Delegation in Cloud Computing

  • September 29, 2015
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Circuit Ciphertext-policy Attribute-based Hybrid Encryption with Verifiable Delegation in Cloud Computing


In the cloud, for achieving access control and keeping data confidential, the data owners could adopt attribute-based encryption to encrypt the stored data. Users with limited computing power are however more likely to delegate the mask of the decryption task to the cloud servers to reduce the computing cost. As a result, attribute-based encryption with delegation emerges. Still, there are caveats and questions remaining in the previous relevant works. For instance, during the delegation, the cloud servers could tamper or replace the delegated ciphertext and respond a forged computing result with malicious intent. They may also cheat the eligible users by responding them that they are ineligible for the purpose of cost saving. Furthermore, during the encryption, the access policies may not be flexible enough as well. Since policy for general circuits enables to achieve the strongest form of access control, a construction for realizing circuit ciphertext-policy attribute-based hybrid encryption with verifiable delegation has been considered in our work. In such a system, combined with verifiable computation and encrypt-then-mac mechanism, the data confidentiality, the fine-grained access control and the correctness of the delegated computing results are well guaranteed at the same time. Besides, our scheme achieves security against chosen-plaintext attacks under the k-multilinear Decisional Diffie-Hellman assumption. Moreover, an extensive simulation campaign confirms the feasibility and efficiency of the proposed solution.


The servers could be used to handle and calculate numerous data according to the user’s demands. As applications move to cloud computing platforms, ciphertext-policy attribute-based encryption (CP-ABE)  and verifiable delegation (VD)  are used to ensure the data confidentiality and the verifiability of delegation on dishonest cloud servers. the increasing volumes of medical images and medical records, the healthcare organizations put a large amount of data in the cloud for reducing data storage costs and supporting medical cooperation. There are two complementary forms of attributebased encryption. One is key-policy attribute-based encryption (KP-ABE)  and the other is ciphertext-policy attribute-based encryption (CPABE).


  • The cloud server might tamper or replace the data owner’s original ciphertext for malicious attacks, and then respond a false transformed ciphertext.
  • The cloud server might cheat the authorized user for cost saving. Though the servers could not respond a correct transformed ciphertext to an unauthorized user, he could cheat an authorized one that he/she is not eligible.


We firstly present a circuit ciphertext-policy attribute-based hybrid encryption with verifiable delegation scheme. General circuits are used to express the strongest form of access control policy. the proposed scheme is proven to be secure based on k-multilinear Decisional Diffie-Hellman assumption. On the other hand, we implement our scheme over the integers. During the delegation computing, a user could validate whether the cloud server responds a correct transformed ciphertext to help him/her decrypt  the ciphertext immediately and correctly.


  • The generic KEM/DEM construction for hybrid encryption which can encrypt messages of arbitrary length.
  • They seek to guarantee the correctness of the original ciphertext by using a commitment.
  • We give the anti-collusion circuit CP-ABE construction in this paper for the reason that CPABE is conceptually closer to the traditional access control methods.





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Jie Xu, Qiaoyan Wen, Wenmin Li and Zhengping Jin, “Circuit Ciphertext-policy Attribute-based Hybrid Encryption with Verifiable Delegation in Cloud Computing”, IEEE Transactions on Parallel and Distributed Systems 2015.

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