Lattice-based Fully Homomorphic Encryption And Access Control,and Its Application In Blockchains

With the development and popularization of blockchain technology,it has become more popular because of its decentralization and openness and transparency.However,in non-public chains,due to users'need for proper supervision and privacy protection,the features of decentralization and transparency are no longer applicable.Access control encryption can not only provide encryption protection for sent messages,but also control the sending and receiving rights of the sender and receiver,so that they cannot send and receive messages without meeting the security policy.Blockchains based on access control encryption may be able to implement node supervision and privacy protection.At the same time,with the continuous development of quantum computers,research on access control encryption schemes with anti-quantum computing capabilities will have great application potential.The main research work of this article is as follows:(1)Fully homomorphic access control encryption is proposed,which can achieve full homomorphic calculation of the message by the receiver while achieving access control encryption and the receiver cannot decrypt the message and the calculation result.A scheme constructing for fully homomorphic access control encryption by nesting is given.This construction method can be implemented on the original access control encryption scheme,but the disadvantage is that the ciphertext is too complicated?(2²⁹)).(2)Based on the access control encryption scheme of TZM17,a fully homomorphic access control encryption scheme based on the error learning problem is constructed,and the correctness and security of the scheme are proved.Compared with the nested construction scheme,the complexity of the ciphertext is greatly reduced?(2⁹)).(3)A system model of fully homomorphic access control encryption scheme and application in blockchains is proposed.In response to the outbreak of COVID-19 in early2020,apply the model to the medical field,a remote diagnosis system model is proposed,and the applicability and security were analyzed.