Implementing RSA Accumulators for Asynchronous and Permissionless Reliable Broadcasting

Asynchronous consensus protocols are critical for decentralized and trustless environments such as decentralized finance, supply chains, and voting systems. These protocols avoid centralized authority and timing assumptions, improving resilience and security. As networks scale communication overhead becomes a major bottleneck limiting performance. The Aleph protocol is a notable example that offers both asynchronous and permissionless Byzantine Fault Tolerance. Unlike many prior designs, Aleph does not depend on a trusted dealer or fixed membership, making it well suited for open blockchain systems. Aleph’s design advances decentralization and security in the blockchain trilemma but at the cost of higher communication complexity and hindering scalability. The Aleph consensus relies on a Chain Reliable Broadcast protocol (ch-RBC) that suffers from quadratic communication overhead in large networks. This study enhances ch-RBC by replacing its Merkle tree-based transaction validation with Rivest–Shamir–Adleman (RSA) accumulators. RSA accumulators provide compact and constant sized proofs that can be batched and parallelized, thus reducing the protocol’s complexity from O(Tr + N² log N) to O(Tr + N²), where T and r denote the number of transactions and rounds respectively. This modification lowers bandwidth consumption and improves scalability while preserving security guarantees. In this study both Merkle and RSA based versions of ch-RBC were implemented in Rust and deployed on AWS EC2 instances using the AWS CDK. Experiments were scaled from 5 to 104 nodes with batch sizes up to 1024 transactions per round. Key metrics included throughput, latency, communication overhead, and resource utilization. Results demonstrated that RSA accumulators significantly improve scalability as the network increases, showing promise for future asynchronous and permissionless consensus.