Although most existing linkable ring signature schemes on lattice can effectively resist quantum attacks, they still have the disadvantages of excessive time and storage overhead. This paper constructs an identity-based linkable ring signature (LRS) scheme over NTRU lattice by employing the technologies of trapdoor generation and rejection sampling. The security of this scheme relies on the small integer solution (SIS) problem on NTRU lattice. We prove that this scheme has unconditional anonymity, unforgeability, and linkability under the random oracle model (ROM). Through the performance analysis, this scheme has a shorter size of public/private keys, and when the number of ring members is small (such as N ≤ 8 ), this scheme has a shorter signature size compared with other existing latest lattice-based LRS schemes. The computational efficiency of signature has also been further improved since it only involves multiplication in the polynomial ring and modular operations of small integers. Finally, we implemented our scheme and other similar schemes, and it is shown that the time for the signature generation and verification of this scheme decreases roughly by 44.951% and 33.503%, respectively.

In order to solve the problem that most of the existing blockchain-based searchable encryption schemes only support exact keyword search and mutual distrust between the cloud server and the user, a searchable encryption scheme based on blockchain, that has functions such as file update dynamically, search results verification, fuzzy keyword search, and fair payment, is proposed. We use edit distance to generate the fuzzy keywords set. According to the un-modification characteristic of Ethereum blockchain and the security of the RSA accumulator, our scheme can verify the search results by the smart contract and realize the service-payment fairness between the user and the cloud server. The security analysis shows that the proposed scheme achieves non-adaptive semantic security. Performance analysis and experiment show that our scheme is efficient and meets the demand of search application in the cloud environment.

Group signatures are active cryptographic topics where group members are granted right to sign messages anonymously on behalf of their group. However, in practical applications, such rights are not permanent in most cases and are usually limited to some time periods. This means that the signing right of each group member needs to be associated with time periods such that it can be automatically changed with the latter. Among the known approaches, verifier local revocation (VLR) seems to be the feasible one to implement the above functionality, but it will cause an inefficient verification process when the group size is large. In this paper, we describe a group signature scheme with time-bound keys, based on the hardness of lattice assumption, which implements the limitation of the signing right to any time period by constructing a lattice-based redactable signature scheme. Our scheme still adds VLR mechanism for some members who need to revoke prematurely, but the time-bound keys function ensures such members are only a small fraction that do not incur excessive cost for revocation check. We give implementation for our scheme under 93-bit and 207-bit security respectively to demonstrate the practicability – all costs are independent of the group size and achieve a relatively efficient level.

There are mostly semi-honest agents in cloud computing, so agents may perform unreliable calculations during the actual execution process. In this paper, an attribute-based verifiable conditional proxy re-encryption (AB-VCPRE) scheme using a homomorphic signature is proposed to solve the problem that the current attribute-based conditional proxy re-encryption (AB-CPRE) algorithm cannot detect the illegal behavior of the agent. The scheme implements robustness, that is the re-encryption ciphertext, can be verified by the verification server, showing that the received ciphertext is correctly converted by the agent from the original ciphertext, thus, meaning that illegal activities of agents can be effectively detected. In addition, the article demonstrates the reliability of the constructed AB-VCPRE scheme validation in the standard model, and proves that the scheme satisfies CPA security in the selective security model based on the learning with errors (LWE) assumption.

In the Internet of Things (IoT) environment, the intelligent devices collect and share large-scale sensitive personal data for a wide range of application. However, the power of storage and computing of IoT devices is limited, so the mass perceived data will be encrypted and transmitted to a cloud platform-interconnected IoT devices. Therefore, the concern how to save the encryption/decryption cost and preserve the privacy of the sensitive data in IoT environment is an issue that deserves research. To mitigate these issues, an offline/online attribute-based encryption scheme that supports partial policy hidden and outsourcing decryption will be proposed. This scheme adopts offline/online attribute-based encryption algorithms; then, the key generation algorithm and encryption algorithm are divided into two stages: offline stage and online stage. Meanwhile, in order to solve the problem of policy disclosure under the cloud platform, the policy hidden is supported, that is, the attribute is divided into the attribute value and the attribute name. For the pairing operation involved in decryption process, a verifiable outsourced decryption is implemented. Our scheme is constructed based on composite bilinear groups, which meets full security under the standard model. Finally, by comparing with other schemes in terms of functionality and computational overhead, it is shown that the proposed scheme is more efficient and applicable to the mobile devices with limited computing and storage functions in the Internet of Things environment.

In an intelligent edge network, data owners encrypt data and outsource it to the edge servers to prevent the leakage of data and user information. It is a research issue to achieve efficient search and data update of the ciphertext stored in the edge servers. For the above problems, we construct a fuzzy multi-keyword search scheme based on a two-level tree index, where the first-level tree index stores keyword tags and the second-level stores encrypted file identifiers and counting bloom filters (CBFs). By constructing a two-level tree index, efficient multi-keyword search is realised, and it also has obvious time advantages when performing the single-keyword search. In addition, the proposed scheme supports index updating by introducing the CBF, and it can realise fuzzy search by calculating the inner product between the CBF in index and search trapdoor. At last, the proposed scheme is proved to be semantically secure under the known ciphertext attack model. Theoretical analysis and simulation test indicate that the proposed scheme spends lower computation overhead than other related schemes, especially in the search phase; as the number of matching files or query keywords grows, it costs less time, at around 2–10 ms.