With the increase of artificial intelligence (AI) agents being used in the operation of digital systems, they can perform complex tasks, manage resources and interact with distributed environments. However, they require additional support in checking the execution, assigning duties and guaranteeing reliability. Therefore, it is difficult to achieve autonomous decision-making along with stable system operation. Consequently, blockchain is regarded not only as a platform for decentralized applications but also as a dependable base for AI agents. Hence, the present blockchain architectures should not only enhance their efficiency but also ensure traceable state modifications, authentic operations and coordinated communications among various AI-related activities. Therefore, our paper investigates the transaction processing and expanding methods from different perspectives. We classify the previous research into five parts: state control and security measures, improvement of sharding, scalability of consensus and Layer-2 architectures, parallel transaction processing systems and application-oriented trading procedures. For each part, we introduce some typical systems, describe their features in design and evaluate the influences on constructing scalable and trustworthy AI agent systems. Besides, we point out the difficulties in establishing the blockchain framework for AI agents. Finally, this survey presents the existing technologies systematically and highlights their importance.

Secure and scalable electronic medical record (EMR) sharing is essential for cross-institutional collaboration, yet existing blockchain-based approaches can incur high on-chain overhead under bursty, fine-grained, and temporary authorization. We propose Secure and Scalable Tokenized EMR Sharing on a Permissioned Blockchain, referred to as SST-MedChain, a patient-centric framework that (i) enables patient-side non-interactive delegation via an Elliptic Curve Diffie–Hellman (ECDH)-derived verification token protected by a hash commitment, and (ii) reduces on-chain authorization to a near constant-time token lookup and atomic state transition using one-time access tokens. SST-MedChain further supports policy-bounded cascading re-delegation and fast revocation over deployment-bounded delegation chains via a Nested Freezing state machine and a Source Circuit Breaker. Experiments on FISCO BCOS (a permissioned blockchain platform) in a wide area network (WAN) show that, on the evaluated on-chain confirmation path, SST-MedChain improves throughput by 38% and reduces latency by 86% compared with Attribute-Based Access Control (ABAC) at 300 queries per second (QPS), and achieves 16.5% higher throughput than MedShare at 1000 QPS with comparatively stable average confirmation latency.

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.