A Searchable Encryption Scheme Based on Lattice for Log Systems in Blockchain

With the increasing popularity of cloud storage,data security on the cloud has become increasingly visible.Searchable encryption has the ability to realize the privacy protection and security of data in the cloud.However,with the continuous development of quantum computing,the standard Public-key Encryption with Keyword Search(PEKS)scheme cannot resist quantumbased keyword guessing attacks.Further,the credibility of the server also poses a significant threat to the security of the retrieval process.This paper proposes a searchable encryption scheme based on lattice cryptography using blockchain to address the above problems.Firstly,we design a lattice-based encryption primitive to resist quantum keyword guessing attacks.Moreover,blockchain is to decentralize the cloud storage platform’s jurisdiction of data.It also ensures that the traceability of keyword retrieval process and maintains the credibility of search result,which malicious platforms are prevented as much as possible from deliberately sending wrong search results.Last but not least,through security analysis,our proposed scheme satisfies the credibility and unforgeability of the keyword ciphertext.The comprehensive performance evaluates that our scheme has certain advantages in terms of efficiency compared with others.

Private membership test protocol with low communication complexity

We introduce a practical method to perform private membership tests.In this method,clients are able to test whether an item is in a set controlled by the server without revealing their query item to the server.After executing the queries,the content of the server's set remains secret.One use case for a private membership test is to check whether a file contains any malware by checking its signature against a database of malware samples in a privacy-preserving way.We apply the Bloom filter and the Cuckoo filter in the membership test procedure.In order to achieve privacy properties,we present a novel protocol based on some homomorphic encryption schemes.In our protocol,we rearrange the data in the set into N-dimensional hypercubes.We have implemented our method in a realistic scenario where a client of an anti-malware company wants to privately check whether a hash value of a given file is in the malware database of the company.The evaluation shows that our method is feasible for real-world applications.We also have tested the performance of our protocol for databases of different sizes and data structures with different dimensions:2-dimensional,3-dimensional,and 4-dimensional hypercubes.We present formulas to estimate the cost of computation and communication in our protocol.

Cryptanalysis of quantum broadcast communication and authentication protocol with a one-time pad

Chang et al.[Chin.Phys.623 010305（2014）]have proposed a quantum broadcast communication and authentication protocol.However,we find that an intercept-resend attack can be preformed successfully by a potential eavesdropper,who will be able to destroy the authentication function.Afterwards,he or she can acquire the secret transmitted message or even modify it while escaping detection,by implementing an efficient man-in-the-middle attack.Furthermore,we show a simple scheme to defend this attack,that is,applying non-reusable identity strings.