Research On Anonymous Encryption For Privacy Protection In Cloud Environment

With the deep development of cloud computing technologies,especially cloud storage technologies,privacy information security has received more and more attention.Privacy information is often private and its leakage causes incalculable losses.At present,the use of cryptography to achieve privacy protection has become one of the current research hotspots.Based on the attribute-based encryption system,this work studies the single attribute authority and the multi-authority(MA).At the same time of considering the anonymity of the public keys and ciphertexts,it also gives a privacy preserving decentralized attribute-based encryption scheme,which realizes the privacy protection of the private key to the attribute authority.The main results are as follows: 1.Privacy preserving attribute-based encryption schemes are proposed.One of them is introduced in the case of the single attribute authority,which is a ciphertext-policy attribute-based encryption scheme with hidden access policies.This scheme not only realizes the hiding of the access policy,but also ensures the privacy of the recipient.In addition,through the decryption testing,the decryption efficiency is improved.And the scheme achieves security of choice under the DBDH assumption.Another scheme is presented in the case of multi-authority.In this scheme,a novel anonymous key generation algorithm based on the oblivious transfer technology is introduced.The user can obtain the private key from the attribute authority without leaking the attribute information,so users' attribute can be hidden in this scheme.At the same time,this scheme realizes the anonymity of the user's global identifier.Compared with the existing multi-authority attribute-based encryption schemes,the proposed MA-ABE scheme not only achieves user privacy protection,but also has low computational cost.2.Two kinds of anonymous attribute-based encryption promotion schemes are proposed.An anonymous attribute-based broadcast encryption scheme and an anonymous attribute-based proxy re-encryption scheme are issued respectively.The first scheme is constructed in the context of composite order bilinear groups,both the access policy and the broadcast list are hidden.In addition,the length of the ciphertexts in this scheme is constant,and the number of pairing in the decryption operation does not change as the number of attributes in the scheme changes.Under three static assumptions,the proposed scheme is full security.The second scheme is proposed by introducing “match then re-encrypt” and “match then decrypt” technologies.This scheme not only realizes the hiding of attributes in the access policy,but also keeps the length of the re-encrypted ciphertext constant.On the premise of not sacrificing computing efficiency,the realization of the anonymous access policy.