Guoyu Yang

Anonymous credential systems (ACs) enable users to selectively disclose attributes in an anonymous and unlinkable manner, but their misuse is hard to address without traceability. Existing traceable ACs introduce regulators to handle this issue, but they impose substantial communication and computational overhead on regulators, especially in complex scenarios involving large numbers of authentication records and multiple independent regulators. In this work, we propose Public-Key Encryption with Equality Test and Variable Public Generator (PKEET-VPG) and its verifiable version (VPV) for adapting to traceable ACs to support secure outsourceable record retrieval from regulators to service providers. The core technical idea is a session-user-level tracing key whose validity is bound to a single authentication session, thereby preventing the abuse of tracing keys.We formally prove that both schemes achieve OW-CCA2 security, and show that, when integrated into ACs, they preserve user anonymity, support non-frameability, and retain cross-session unlinkability. Theoretical analysis and comparative experiments demonstrate that our schemes can reduce the overhead of regulators at a moderate cost in the authentication phase. Furthermore, our schemes support session-level ciphertext deduplication, which may be of independent interest in some scenarios, such as anonymous voting or one-action-per-session authentication.

The widespread deployment of Internet of Things (IoT) devices has driven their segmentation into distinct trust domains for the purpose of governance, creating a critical need for secure cross-domain authentication (CDA). CDA must preserve both anonymity and traceability of device identities to enable trustworthy data exchange. However, existing approaches, while exploring this trade-off, remain vulnerable to single points of failure and Sybil attacks—threats that are especially severe for unattended and resource-constrained devices. In this paper, we propose a Self-Sovereign and Supervised Cross-domain authentication scheme (SCross) to tackle these issues. The main building block we designed is a pseudonym management scheme (PMS) that allows devices to generate and use pseudonyms without relying on a trusted party. Although devices has full control of their identities, PMS still ensures traceability, Sybil resistance, and revocability. We define the formal security models of PMS, instantiate it under two different approaches, namely group signature (SCross-GS) and zero-knowledge succinct non-interactive arguments of knowledge (zkSNARKs, SCross-ZK), and present security proofs for our proposal. We implemented and evaluated SCross. The result shows that our scheme achieves an effective trade-off between security and efficiency.

Asynchronous common subset (ACS) is an essential building block for Byzantine fault-tolerance and multi-party computation. The classic ACS framework is due to Ben-Or, Kemler, and Rabin (BKR), consisting of n reliable broadcast (RBC) instances and n asynchronous binary agreement (ABA) instances (where n is the total number of replicas). Despite recent progresses of practical BKR-ACS, the state-of-the-art designs are still trapped by a validity-latency tradeoff. In this paper, we propose Sweeper, a new ACS protocol that breaks the tradeoff, achieving optimal validity and latency. Moreover, Sweeper maintains other benefits including optimal resilience, signature-free, and information-theoretic settings. Sweeper is built on RBC and composable biased reproposable ABA (CBiased RABA). Different from the conventional RABA, CBiased RABA allows replicas to be more biased towards specific RABA instances. We provide generic strategies to transform existing ABA/RABA protocols and a new RABA protocol that we introduce, to CBiased RABA. Furthermore, Sweeper can achieve up to 2× the throughput of PACE-ACS (CCS 2022), the state-of-the-art ACS protocol that follows the BKR-ACS framework.

Cross-chain transaction technologies have greatly promoted the scalability of cryptocurrencies, which then facilitates the development of Metaverse applications. However, existing solutions rely heavily on centralized middleware (notary) or smart contracts. These schemes lack privacy considerations, and users’ cross-chain transactions are easy to master by other parties. Some signature-based payment schemes have good privacy but do not support multi-party cross-chain protocols or rely heavily on some time assumptions. The uncertainty of user behavior makes it difficult to design a secure multi-party cross-chain protocol. To solve these problems, we investigate how to design a secure multi-party cross-chain transaction protocol with offline tolerance. We propose a new signature algorithm called the pre-adaptor signature scheme, an extension of the adaptor signature scheme. The pre-adaptor signature scheme combines the multi-signature and adaptor signature schemes, which can realize the secret transmission channel between multiple parties. To provide offline tolerance, we encode our protocol into the P2SH script. Our protocol provides better privacy due to no dependence on smart contracts. The performance evaluation was conducted with ten participants. For each participant of our cross-chain protocol, the initialization and execution process can be performed in 3 milliseconds and with 6 k bytes of communication overhead at most. The cost increases linearly with the increase in the number of participants.

Advances in machine learning (ML) in recent years have enabled a dizzying array of applications such as data analytics, autonomous systems, and security diagnostics. As an important part of the Internet of Things (IoT), wireless sensor networks (WSNs) have been widely used in military, transportation, medical, and household fields. However, in the applications of wireless sensor networks, the adversary can infer the location of a source node and an event by backtracking attacks and traffic analysis. The location privacy leakage of a source node has become one of the most urgent problems to be solved in wireless sensor networks. To solve the problem of source location privacy leakage, in this paper, we first propose a proxy source node selection mechanism by constructing the candidate region. Secondly, based on the residual energy of the node, we propose a shortest routing algorithm to achieve better forwarding efficiency. Finally, by combining the proposed proxy source node selection mechanism with the proposed shortest routing algorithm based on the residual energy, we further propose a new, anonymous communication scheme. Meanwhile, the performance analysis indicates that the anonymous communication scheme can effectively protect the location privacy of the source nodes and reduce the network overhead.