Remote Procedure Call (RPC) services have become a primary gateway for users to access public blockchains. While they offer significant convenience, RPC services also introduce critical privacy challenges that remain insufficiently examined. Existing deanonymization attacks either do not apply to blockchain RPC users or incur costs like transaction fees assuming an active network eavesdropper. In this paper, we propose a novel deanonymization attack that can link an IP address of a RPC user to this user's blockchain pseudonym. Our analysis reveals a temporal correlation between the timestamps of transaction confirmations recorded on the public ledger and those of TCP packets sent by the victim when querying transaction status. We assume a strong passive adversary with access to network infrastructure, capable of monitoring traffic at network border routers or Internet exchange points. By monitoring network traffic and analyzing public ledgers, the attacker can link the IP address of the TCP packet to the pseudonym of the transaction initiator by exploiting the temporal correlation. This deanonymization attack incurs zero transaction fee. We mathematically model and analyze the attack method, perform large-scale measurements of blockchain ledgers, and conduct real-world attacks to validate the attack. Our attack achieves a high success rate of over 95% against normal RPC users on various blockchain networks, including Ethereum, Bitcoin and Solana.

The Internet of Things (IoT) has built an information bridge between people and the objective world, wherein wireless sensor networks (WSNs) are an important driving force. For applications based on WSN, such as environment monitoring, smart healthcare, user legitimacy authentication, and data security, are always worth exploring. In recent years, many multifactor user authentication schemes for WSNs have been proposed using smart cards, passwords, as well as biometric features. Unfortunately, these schemes are revealed to various vulnerabilities (e.g., password guessing attack, impersonation attack, and replay attack) due to nonuniform security evaluation criteria. Wang et al. put forward 12 pieces of widely accepted evaluation criteria by investigating quantities of relevant literature. In this paper, we first propose a lightweight multifactor authentication protocol for multigateway WSNs using hash functions and XOR operations. Further, BAN logic and BPR model are employed to formally prove the correctness and security of the proposed scheme, and the informal analysis with Wang et al.’s criteria also indicates that it can resist well-known attacks. Finally, performance analysis of the compared schemes is given, and the evaluation results show that only the proposed scheme can satisfy all 12 evaluation criteria and keep efficient among these schemes.