Multi-authorization Attribute-based Encryption Research

Attribute-based encryption(ABE)implements a new type of many-to-many encryption mode.In the ABE schemes,the public key is a set of descriptive attributes.Besides,it use the access strategy to achieve the goal that every user who meets the corresponding conditions can decrypt the ciphertext.The decryption user is no longer a single individual,but a group.Based on this feature,attribute-based encryption can be widely used in distributed environment,such as secure storage in cloud computing.In the early attribute-based encryption scheme,there is only one authority to manage the attributes,calculate the keys and send them to different users.The workload and burden is heavy.Once the authority is compromised,all private keys are compromised,so the risk is greater.In order to solve the above problem,in 2007 Chase first proposed multi-authority attribute-based encryption system.In this scheme,although there are multiple authorities working together,but still need a credible central authority to manage the set of authorities.So the security bottlenecks are still present,once the central authority were broken,the system security is threatened.In 2013,Li et al.proposed a fully secure distributed attribute-based encryption scheme.It removes the security bottleneck,but its decryption efficiency is low.Therefore,in 2015,Longo et al.proposed the multi-authority attribute-based encryption scheme without the central authority(MA-KP-ABE).The advantage of this scheme is that every algorithm is very simple and the decryption efficiency is relatively high.This paper focus on the multi-authority attribute-based encryption system,especially the scheme proposed by Longo et al..The main work is divided into the following two parts:1)Aiming at two shortcomings in Longo’s scheme,we present a multi-authority attribute-based encryption scheme with key verification.Firstly,Longo’s scheme can not prevent the collusion.We know that the basic security requirement of a multi-authority ABE scheme is that it must resist collusion attacks.So this is a serious problem.Secondly,it can not verify the user’s private key is correct or not.If the user can not successfully decrypt,all the authorities have to re-issue private key.Our new scheme can resist the collusion attack,and realize the verification of the correctness of the user’s private key by using the key verifiable idea.2)In most of the current ABE solution,the decryption efficiency is relatively low,it needs calculate a bilinear pair for each decryption attribute.And it also exist the protection problem of user’s privacy,authority can unite to reveal the user’s attribute set.Under the framework of Longo’s MA-KP-ABE,we present a new privacy-protecting multi-authority attribute-based encryption scheme with fast decryption by combining the anonymous key issuing and the fast decryption idea.The new scheme can guarantee the security of the user’s privacy,using the anonymous key issuing protocol,the authority does not know the user’s global unique identity(GID)at all,when the user ask the decryption key,avoiding the authorities to track user’s attributes information according to the user’s GID,so that the user’s privacy has been protected.At the same time,the decryption process,for a single authority,only need to calculate two bilinear parings,greatly reducing the amount of computation of bilinear parings,improving the decryption efficiency,realizing the fast decryption.