Secure and efficient identity authentication is a fundamental requirement in vehicular ad-hoc networks (VANETs); however, it remains challenging due to the highly dynamic network topology, stringent latency constraints, and the need for conditional privacy preservation. Existing authentication schemes either rely on public key infrastructures (PKI) with complex certificate management or introduce partially decentralized designs that still depend on trusted authorities, leading to inefficiencies and single points of failure. In this paper, we propose EBDA, an Ethereum-based fully distributed authentication mechanism for VANETs. The core innovation of EBDA is to replace the traditional PKI certificate system with a blockchain-maintained Graph of Trust (GoT). Through three dedicated smart contracts, EBDA  fully decentralizes the management of vehicle identities and pseudonyms. Vehicles use pseudonyms to preserve privacy in Vehicle-to-Vehicle communications, while authentication is achieved certificate-free via transitive trust within the GoT. Importantly, latency-sensitive operations like message verification are executed off-chain through local checks, meeting VANETs’ strict real-time requirements. A prototype implementation and extensive evaluations demonstrate that EBDA significantly reduces authentication latency by at least 22.93% compared with representative blockchain-assisted and PKI-based baselines while maintaining low computational and storage overhead. These results confirm the feasibility of deploying GoT-based decentralized authentication in practical VANET environments.

The Bitcoin system has operated reliably for over 16 years, attracting considerable attention due to its decentralized architecture and the inherent value of its digital assets. Nevertheless, performance limitations, especially in transaction validation, continue to impede its scalability and efficiency. In the Bitcoin network, each full node not only needs to validate a transaction when it is first received, but also needs to validate it again when it is packaged into a new block. This redundant validation mechanism reduces the overall efficiency of the Bitcoin system. Utilizing Segregated Witness technology, this paper introduces a one-time validation optimization scheme. Specifically, we leverage the Witness Transaction ID (wtxid) inherent in SegWit to build a deterministic index mapping between the local transaction pool and new candidate blocks. By checking this index, the system can identify and skip the redundant verification of transactions that have already been validated upon entry into the pool. The proposed approach eliminates the need for secondary validation when processing new blocks, specifically for transactions already stored in the local transaction pool. Through comprehensive theoretical analysis, we demonstrate that this optimization can reduce the transaction validation overhead by approximately 50% without compromising the security of the Bitcoin network. In short, our research provides an innovative solution to Bitcoin’s performance challenges, thereby contributing to its future development and long-term sustainability.

Cryptocurrency is a novel exploration of a form of currency that proposes a decentralized  electronic payment scheme based on blockchain technology and cryptographic theory. While blockchain has the security characteristics of being distributed and tamper-proof, increasing market demand has led to a rise in malicious transactions and attacks, thereby exposing cryptocurrency to vulnerabilities,  privacy issues, and security threats. Particularly concerning are the emerging types of attacks and threats, which have made securing cryptocurrency increasingly urgent. This paper classifies existing cryptocurrency security threats and attacks into five fundamental categories based on the blockchain infrastructure, and it analyzes in detail the vulnerability principles exploited by each type of threat and attack. Furthermore, the paper examines the attackers’ logic and methods and provides insights that enable easy reproduction of the vulnerabilities. We also summarize and evaluate existing detection and defense solutions, offering important references for ensuring cryptocurrency security. Finally, the paper discusses the future development trends of cryptocurrency.