Multi-signature is a typical digital signature for signing one message by multiple signers. Its advantage is that the length of the signature is independent of the number of signers, even though multiple users sign the same message. It can therefore serve as a fundamental building block in many secure multiple computation scenarios, e.g., signing a transaction in blockchain applications, signing a routing message in routing discovery protocols, and so on. Nonetheless, most of the existing multi-signature schemes have been still based on traditional signatures over the hardness of number theory problems such as integer factoring or discrete logarithm, which may be insecure in future quantum computing environment. Besides, they impose the cost of public key infrastructure due to the authentication of public keys. Instead, identity-based (ID-based) signature can avoid such overhead due to the management of public keys by using a public identity as a public key. Therefore, in this paper we propose a broadcast multi-signature scheme that is ID-based and lattice-based (i.e., with the hardness assumption on solving lattice problems). Our scheme has the advantages from not only ID-based signatures but also lattice-based signatures. Moreover, the scheme is efficient as the signature length is short, which is suitable for length sensitive applications, e.g., signing transactions in a blockchain.

Real-time kinematic (RTK) positioning is a widely used technique that improves positioning accuracy to the centimeter level. In RTK systems, users can utilize the correction data provided by a reference station (RS) to offset their location errors. However, due to the limited deployment and high cost of RS, some places are not covered by physical RS (within 30 kilometers). Therefore, a virtual reference station (VRS) RTK service is provided, where a server generates VRS for users and provides seamless cloud-based network RTK corrections without the need of a real RS. Despite the benefits of VRS services, it poses a risk to user location privacy, as users need to continuously report their standalone calculated positions to the server to obtain the service. In this paper, we propose a privacy-preserving approach for VRS services by multicasting correction data over mobile networks, where joined users can receive valid correction data from the base station in either inactive or connected mode. Experiment results show that the network delay is less than 40ms, throughput is about 16kbps, and the RTK positioning error is 4cm. Other qualitative analyses (such as service continuity and stability) also prove the feasibility and effectiveness of the proposed method.

Current solutions on cross-domain access authentication based on blockchain are largely using digital certificate authentication, where users cannot control their identity, and some operations, such as certificate authentication and update, are inefficient. In this paper, we propose a Self-Sovereign Identity (SSI) based cross-domain authentication scheme implemented on a consortium chain. SSI is introduced as a decentralized digital identity solution to enable user-controlled identity management. Besides, blockchain, as an infrastructure for distributed digital identity, provides a storage place for decentralized identity identifiers and related data. In our scheme, users only need to register in one domain, and can use verifiable credentials (VC) to access other domains in the same consortium chain, without repeated registration. We also propose key method for quickly changing accounts in case of account loss. The logic, performance and security analysis justified that our scheme can protect the privacy of users and can remain feasible in case of a large scale of users.

Blockchain can be envisioned as an enabling framework in terms of cryptography and distributed computing to construct trusted data records among un-trusted users. It can be applied in two typical scenarios - historical process provenance and transaction tracing, by immutably sequentialized blocks. In the former there exists no tokens; but in the latter token handover among accounts should be cryptographically guaranteed. In some situations, above two applications may be both required. E.g., in the manufacture of a jewel, processing flow by different operators should be recorded for quality guaranteeing, and in its trading stage, the ownership handover should be recorded for value confirmation. To tackle above two requirements, two chains are usually thus demanded. In this paper, we propose a single chain solution to avoid cross-chain burden, by a hybrid block structure. The process data can be imported from the legacy (non-anonymous) information processing system, and transaction data stems from anonymous payment demand for ownership handover. We formally describe and prove token handover model with cryptographical authenticity. We also propose several security enhancements in the design for shortening the length of the chain, and protecting the data confidentiality in the chain. Our design is general and not limited to single application. The experimental results and extensive analysis justified that the performance and security of our proposed scheme is efficient.

Thanks to mobility and large coverage, 6G mobile networks introduce satellites and unmanned aerial vehicles as aerial base stations (ABS) in the 6G era. Instead of using a wired backhaul in 5G and its predecessor, an ABS leverages a wireless channel to a core network (CN). However, such a wireless channel design introduces new security challenges. In this paper, we present that passive attackers could sniff the ABS-CN wireless channel and identify what users are doing based on deep learning methods. We collect GTP protocol data on our testbed and use convolutional neural networks to classify 5 types of encrypted App traffic, like IG and TikTok. Experiment results proved the effectiveness of the proposed method, revealing the confidential data leakage problem on the 6G wireless ABS-CN channel.

Blockchain has been envisioned as an anonymous cryptocurrency framework and can be applied in various applications such as e-payment, share economics, and distributed ledger. Although an account is anonymous, privacy in terms of consumption behaviors still imposes leakage risks. For example, an adversary may infer the consumption capability related to an account further by analyzing the history of consumption records. It is thus of critical importance to design a solution to preserve the anonymity of both transaction amount and transaction peer’s identity, which is changeable because the amount must be still authenticated in anonymity. In this paper, we propose a scheme by using Pedersen commitment to anonymize the transaction amount, and together using ring signature to conceal the transaction peer’s identity while maintaining authentication. Especially, we further improve the security of anonymous authentication enabled by ring signature by introducing accountability, which can defend against double-spending attacks by penalization and empower auditability. The extensive performance and security analysis justify the applicability of the proposed scheme.

In large-scale Internet of Things (IoT) systems, centralized authentication can be challenging, for example in terms of identity management, authentication overhead, and single point of failure. Distributed identity management has been envisioned as a promising approach for mitigating above all, but the security and performance of the overall solution have not been extensively evaluated. In this article, we proposed a decentralized identity management scheme based on blockchain for tackling large-scale IoT such as VANET. We implement smart contracts to support large-scale user access control, together with design trust management methods for reputation evaluation and credit penalty mechanisms, which can prevent various types of attacks in distributed identification contexts. The experiment results and analysis justified that our scheme is scalable with good performance. Specifically, the system response is on a millisecond scale and all the functions consume within 250 ms. Also, the time consumption of the query maintains a manageable delay within 0.5 ms no matter the remarkable growth of users. Finally, we observe that the throughput of the current blockchain platform could meet the requirement of our scheme with the increasing number of users’ upload request in real-world simulation.

Internet-of-Things (IoT) are increasingly operating in the zero-trust environments where any devices and systems may be compromised and hence untrusted. In addition, data collected by and sent from IoT devices may be shared with and processed by edge computing systems, in order to reduce the reliance on centralized (cloud) servers, leading to further security and privacy issues. To cope with these challenges, this paper proposes an innovative blockchain-enabled information sharing solution in zero-trust context to guarantee anonymity yet entity authentication, data privacy yet data trustworthiness, and participant stimulation yet fairness. This new solution is able to support filtering of fabricated information through smart contracts, effective voting, and consensus mechanisms, which can prevent unauthenticated participants from sharing garbage information. We also prove that the proposed solution is secure in the universal composability framework, and further evaluate its performance over an Ethereum-based blockchain platform to demonstrate its utility.