BlockA2A: Towards Secure and Verifiable Agent-to-Agent Interoperability

TL;DR

This paper introduces BlockA2A, a comprehensive framework that enhances security and verifiability in multi-agent systems powered by large language models, addressing key vulnerabilities with decentralized and blockchain-based solutions.

Contribution

It presents the first unified trust framework for secure agent-to-agent interoperability, integrating decentralized identifiers, blockchain ledgers, and smart contracts, along with a real-time attack mitigation engine.

Findings

BlockA2A effectively neutralizes various MAS attacks.

The framework operates with sub-second overhead.

Practical implementation demonstrates scalability and security enhancements.

Abstract

The rapid adoption of agentic AI, powered by large language models (LLMs), is transforming enterprise ecosystems with autonomous agents that execute complex workflows. Yet we observe several key security vulnerabilities in LLM-driven multi-agent systems (MASes): fragmented identity frameworks, insecure communication channels, and inadequate defenses against Byzantine agents or adversarial prompts. In this paper, we present the first systematic analysis of these emerging multi-agent risks and explain why the legacy security strategies cannot effectively address these risks. Afterwards, we propose BlockA2A, the first unified multi-agent trust framework that enables secure and verifiable and agent-to-agent interoperability. At a high level, BlockA2A adopts decentralized identifiers (DIDs) to enable fine-grained cross-domain agent authentication, blockchain-anchored ledgers to enable immutable auditability, and smart contracts to dynamically enforce context-aware access control policies. BlockA2A eliminates centralized trust bottlenecks, ensures message authenticity and execution integrity, and guarantees accountability across agent interactions. Furthermore, we propose a Defense Orchestration Engine (DOE) that actively neutralizes attacks through real-time mechanisms, including Byzantine agent flagging, reactive execution halting, and instant permission revocation. Empirical evaluations demonstrate BlockA2A's effectiveness in neutralizing prompt-based, communication-based, behavioral and systemic MAS attacks. We formalize its integration into existing MAS and showcase a practical implementation for Google's A2A protocol. Experiments confirm that BlockA2A and DOE operate with sub-second overhead, enabling scalable deployment in production LLM-based MAS environments.