Blockchain systems have evolved over decades, addressing the inefficiencies and high costs associated with centralized architectures. Among various consensus mechanisms, committee-based hybrid Byzantine Fault Tolerant (BFT) protocols are a fundamental approach to blockchain consensus. However, designing a hybrid BFT consensus protocol that ensures fairness, responsiveness, and formal security remains challenging. In this paper, we propose GRBFT: a Gaussian reputation-based hybrid BFT blockchain consensus protocol with a formal security framework. Our proposed protocol integrates a multilateral Gaussian reputation evaluation to incentivize trusted nodes' participation in the consensus. We use threshold signatures and verifiable random functions (VRFs) to randomly select committee members and leaders, ensuring fair reconfiguration and unbiased sortition. A formal security framework is utilized to design and analyze the blockchain consensus system. Additionally, we design a speculative GRBFT (S-GRBFT) protocol to circumvent the traditional$\mathcal {O}(n^{2})$leader sortition complexity and reduce the communication to$\mathcal {O}(n)$within a single round. Moreover, we present a secure candidate committee reconfiguration method that efficiently updates members based on their reputation and a Proof-of-Stake (PoS) mechanism. The proposed GRBFT protocol is proven to achieve consistency and liveness under the corruption and liveness parameters.

Committee-based blockchain consensus is a fusion of permissionless consensus and the permissioned Byzantine Fault- Tolerant (BFT) classical protocol. However, three enduring challenges remain: the formal framework for the Proof-of-Stake (PoS)-based hybrid consensus, the dynamic adjustment of committee size and the definition of consensus time-bound. To tackle these challenges, in this paper, we present a Stackelberg game-driven fair committee-based blockchain consensus protocol, dubbed SG-FCB, which combines PoS and reputation-based blockchain hybrid BFT consensus. The SG-FCB protocol lever-ages an unbiased BLS-threshold signature and a random shuffle algorithm to achieve fair leader election and committee reconfiguration seamlessly. Specifically, the variant-BFT is designed to maintain the low communication cost of$\mathcal{O}(n)$, and a Stackelberg game-based incentive mechanism is proposed to jointly maximize the individual profit of the validators and the expected consensus committee responsiveness efficiency of blockchain user. Rigorous security analysis shows that for an adversary with a stakeholding fraction less than 1/3 and sufficient reputation value, we define the time bound for consensus, and the SG-FCB protocol achieves consistency and liveness properties by reasonably setting a corruption parameter and liveness parameter within a formal framework.

The technology for securely sharing data has grown extensively in recent years. Many users are willing to share their lightweight mobile device data via social networks or the cloud. A novel matchmaking encryption primitive was proposed in CRYPTO’19, whose potential for privacy protection and data sharing security was introduced. However, matchmaking encryption technology faces challenges in flexibly realizing critical functions, such as one-to-many non-interactive scenarios, no key escrow problem, stronger security, lightweight computation and low communication overheads for mobile devices, which impede their widespread application. To achieve the above functions, we present a lightweight certificateless multi-user matchmaking encryption (LC-MUME) for mobile devices, which enhances security flexibly and performance based on standard hard assumptions and low-consumption pairing-free technology, while also avoiding one-by-one encryption for each user. The proposed LC-MUME scheme enjoys minor computation and communication overheads in a one-to-many non-interactive certificateless cryptosystem. We prove that our scheme achieves indistinguishability-based chosen-ciphertext attack (IND-CCA) security, the existential unforgeability under a chosen message attack (EU-CMA) security and anonymity-CCA security under the random oracle model. Our LC-MUME scheme outperforms the state-of-the-art schemes regarding efficiency and flexibility, as demonstrated by the performance comparison and analysis, and therefore is a practical solution for resource-constrained mobile devices.

Vehicular ad hoc networks (VANETs) establish wireless connections among all vehicles, enabling seamless mobile communication. However, existing conditional privacy protection VANETs authentication schemes fail to address the issue of potential key-exposure and do not provide accelerated vehicle authentication. In this paper, we propose a reputation incentive committee-based secure conditional dual authentication scheme for VANETs called RIC-SDA. Our proposed scheme incorporates dual authentication of the consensus committee and vehicle-to-vehicle (V2V) communication. It enables the rapid provision of dynamic vehicle epoch-key from consensus committee authentication for V2V authentication through our designed reputation incentive mechanism. To mitigate the potential key-exposure problem, we introduce a novel concept of secure vehicle epoch communication, which means V2V authentication is valid for only one epoch blockchain unit time. The proposed scheme achieves lightweight computation and incurs minimal communication overheads, with the signature size being just 137 bytes. The RIC-SDA scheme supports fast batch verification. We prove that our proposed scheme is unforgeable security under random oracle and demonstrate its feasibility by implementing it in a test network based on Ethereum Sepolia. The results demonstrate that our RIC-SDA solution outperforms the existing state-of-the-art authentication VANET schemes regarding efficiency and communication costs.

Matchmaking encryption is a method employed to address the security and privacy concerns of cloud-enabled IoT healthcare. Nevertheless, matchmaking encryption technology encounters challenges in effectively implementing critical functionalities, such as resolving a single-key-exposure problem, achieving secure short-epoch communication, and simultaneously enabling lightweight computation and communication overheads for IoT healthcare. These challenges pose obstacles to the widespread adoption of this technology. To tackle these constraints, we first present aReputation incentive committeeConsensus-based forMatchmakingEncryption in IoT healthcare (RCME), which utilizes consensus nodes to eliminate the single-key-exposure problem and enables fast provision of permission proof based on our design reputation incentive mechanism. The proposed RCME scheme adopts low-consumption pairing-free technology to realize lightweight matchmaking encryption in a multi-party, non-interactive certificateless cryptosystem. Rigorous security analysis shows it achieves chosen ciphertext attack security under the random oracle model. To further reduce consensus communication overhead from$\mathcal {O}(n^{2})$to$\mathcal {O}(n)$, we propose an optimized Practical Byzantine Fault Tolerance (PBFT) consensus, and we adopt reputation incentive mechanism and threshold cryptography technology to achieve unbiased leader election. The comprehensive evaluation corroborates that our solutions outperform the existing state-of-the-art schemes regarding security and performance. Therefore, our RCME scheme is a practical solution for resource-constrained IoT healthcare devices.

The Industrial Internet of Things (IIoT) and cloud computing have developed rapidly in recent years. Many enterprises are willing to outsource lightweight devices’ industrial data via the cloud to lower manufacturing costs and enhance production efficiency. The data sharers, however, usually have concerns about the security and privacy of their data stored in cloud outsourcing systems. Traditional certificateless searchable encryption primitives are tough to realize dynamically revocable and high-efficiency decryption. Furthermore, data sharing on untrusted devices may cause a single-key exposure problem. To address these issues, we propose a blockchain-assisted secure data-sharing protocol with a dynamic multiuser keyword search (DMUKS) in IIoT, which utilizes blockchain-assisted techniques to solve a single-key exposure problem and to realize fast certificateless keyword search as well as dynamic user and key management. The proposed DMUKS scheme enjoys minor computation and communication overheads. It maintains a constant ciphertext and trapdoor query size as users increase and supports user addition and revocation. Moreover, it periodically supports key and ciphertext updating and is secure against keyword-guessing attacks under the random oracle model. The performance comparison and analysis demonstrate that it is more efficient and flexible than the existing data sharing with keyword search schemes.

Data management services provided by the public cloud can economize the enterprise’s local storage costs, and meanwhile, realize data sharing among the enterprise. Corporate users, however, usually have concerns about the security and privacy of their data stored in the public cloud. Searchable encryption has been used as a secure method for enterprise users in the public cloud to share data via keyword search for many years. Nevertheless, conventional search and encryption primitives are challenging to realize several critical functions flexibly, such as key update, user revocation, lightweight computation, and low communication overhead for users, which will impede their widespread application. Besides, it may cause single-key-exposure security concerns by using untrusted devices. To address these issues, we present a dynamic consensus committee-based for secure data sharing with authorized multi-receiver searchable encryption (called DCC-SE), which exploits the blockchain dynamic committee to eliminate a single-key-exposure problem and enables fast keyword search without pairing and dynamic user management. The proposed DCC-SE scheme enjoys minor computation and communication overheads. It maintains a constant ciphertext size as the receiver increases. Furthermore, it periodically supports secure key and ciphertext updating and has been proven secure against chosen plaintext attacks and the chosen keyword guessing attacks under the random oracle model. The performance evaluation results show that DCC-SE has more feasibility and higher efficiency than the previous public key with keyword search(PEKS) schemes through theoretical analysis and simulation studies.