Due to limited computational and storage capabilities, wireless medical sensor networks (WMSN) encounter considerable overhead in processing the storage and verification of numerous signatures. Multi-signatures allow a group of signers to produce a single, compact signature on the same message, significantly reducing storage requirements and communication bandwidth in WMSN. However, conventional multi-signature schemes are not quantum resistant, as their security assumptions will be compromised with the quick advancement in quantum computing. Alternatively, lattice-based cryptography is widely considered capable of withstanding quantum computing attacks. In this article, we introduce a quantum-resistant and non-interactive identity-based multi-signature scheme from lattices with public key aggregation (IBMS-pka). By leveraging the small integer solution (SIS) assumption, our scheme is proven secure within the random oracle model. Besides, our scheme enables users to choose their system identities (e.g., physical IP address or email address) as public keys compared to PKI-based schemes, and avoids the extra communication costs in contrast to interactive schemes. Meanwhile, our scheme outperforms other related works according to our experiments. Specifically, the multi-signature generation has a slightly higher efficiency compared to other related schemes, while the multi-signature verification has a larger enhancement. Moreover, the performance improvement becomes more evident as the number of signers grows.

To reduce data storage costs, more individuals are using cloud servers for reliable, scalable, cost-effective, and globally accessible solutions. However, storing data in plaintext on cloud servers can lead to data leakage risks. Moreover, the advancement of quantum computing poses a threat to traditional encryption algorithms. To counter quantum computing attacks and enable searches over encrypted keywords, lattice-based searchable encryption with conjunctive keyword search has been implemented. Nonetheless, existing schemes expose keyword fields and leaks additional information. To mitigate this, we propose a privacy-preserving method based on lattice hardness assumptions. It enables testing the existence of an encrypted keyword in a set of encrypted keywords without requiring the keyword fields. Additionally, we propose two improved methods: one for inclusion-based searches between two keyword sets, and another for range-based keyword searches. These form the basis for three lattice-based identity-based searchable encryption schemes that support disjunctive, conjunctive, and range keyword searches, respectively. The storage overhead of ciphertexts and trapdoors is unaffected by the number of keywords, making our scheme suitable for multi-keyword search scenarios. Our formal security analysis uses the learning with errors (LWE) assumption and our theoretical analysis and experimental simulations show comparable efficiency and low storage overhead.

Abstract A forward-secure group signature (FSGS) ensures the unforgeability of signatures in the past time period despite signing secret key is leaked in the current time period. As we know, traditional FSGS schemes are mostly relying on number-theoretic assumptions unable to resist quantum attacks. Therefore, we present an efficient lattice-based fully dynamic (i.e. users can flexibly join or quit the group) forward-secure group signature (DFSGS) by combining an improved version of FSGS scheme proposed by Ling. Based on an efficient zero-knowledge argument, we construct argument of knowledge of the committed value and the plaintext that help with privacy protection. Our DFSGS scheme is proved to be anonymous and forward-secure traceable relying on short integer solution and learning with errors assumptions in random oracle model. Moreover, the lengths of group public key and signature of our DFSGS scheme have been improved, and the length of user secret key has no connection with the quantity of group members.

Abstract Functional encryption (FE) is a novel paradigm for encryption scheme which allows tremendous flexibility in accessing encrypted information. In FE, a user can learn specific function of encrypted messages by restricted functional key and reveal nothing else about the messages. Inner product encryption (IPE) is a special type of functional encryption where the decryption algorithm, given a ciphertext related to a vector x and a secret key related to a vector y, computes the inner product x·y. In this paper, we construct an efficient private-key functional encryption (FE) for inner product with simulation-based security, which is much stronger than indistinguishability-based security, under the External Decisional Linear assumption in the standard model. Compared with the existing schemes, our construction is faster in encryption and decryption, and the master secret key, secret keys and ciphertexts are shorter.