Research And Application Of Revocable Encryption

With the gradual increase of all kinds of information that is transmitted via the network,how to ensure the confidentiality of the digital information has always been the focus of public attention.By considering this,public key encryption technology,an important measure to assure information security,provides a reliable guarantee for the secure transmission of the diversified digital information.Furthermore,the emergence of cloud computing technology enables the possibility of on-demand storage and instant access to user data.However,due to the public known untrusted nature of the third-party cloud servers,how to keep the forward security of user's data stored on the cloud servers is still challenging.In order to overcome this challenge,in recent years,the cryptographic system that supports user revocation arises and has obtained great focus from industrial and academic experts.In view of the significance of revocable encryption technology for industrial production and academic research,in this thesis,the following contributions are achieved after studying the revocable encryption methodology and its application in-deep:An attribute-based encryption work that enables both efficient access policy expression and user revocation for the cloud-assisted Internet of Things(Io T)is presented in this thesis.In the presented scheme,the Arithmetic Span Program is used to simplify the expression of complex data access control policy to obtain better efficiency in terms of data encryption.Moreover,considering the demand for user revocation in Io T scenario,the indirect revocation mechanism is also introduced in the proposed scheme to handle the issue of user revocation.At the same time,in light of the public known untrusted nature of the third-party cloud servers,in the proposed scheme,the data uploaded by users will be periodically updated.In this case,the confidentiality of these data can be effectively assured even if the user's decryption key is leaked.The adaptive security of the presented work is demonstrated via the dual-system encryption methodology.Compared with the existing attribute-based encryption schemes that support user revocation,the proposed scheme is superior to these works in terms of security and efficiency.A fully secure and unbounded attribute-based encryption scheme that supports direct user revocation in Io T is constructed in this thesis.In the presented scheme,it is not necessary to pre-define the attribute-related public parameters involved in the system.Therefore,the proposed work can be dynamically adjusted according to the actual needs in real-life applications,even if it has been deployed.Moreover,compared with the existing schemes,the size of the user revocation list in the proposed scheme is tiny and always keeps constant.Hence,it causes no additional computing and communicating overheads,even if the number of revoked users in this system grows.The full security of the proposed scheme depends on the standard decision linear hypothesis.Compared with the existing attribute-based encryption scheme that supports direct user revocation,the proposed scheme performs betters in terms of security,efficiency and practicability.