From PBFT to Blockchain: A Comprehensive Survey of Byzantine Fault-Tolerant Consensus

Abstract

Byzantine Fault Tolerance (BFT) has developed from a theoretical concept in distributed database reliability to the basic structure of today's decentralized finance and global infrastructure. This paper provides a holistic overview of BFT approach, delineating imperative strides from classical synchronous resolutions to the most recent blockchain protocols. We give a formal treatment of the transition of the architecture from quadratic complexity (O(n2)) in PBFT to linear scalability$(O(n))$in HotStuff and probabilistic guarantees, as compared with Nakamoto Consensus. Moreover, we present a critical review of some recent developments in 2024 and 2025 related to Machine Learning-accelerated adaptive consensus, probabilistic relaxation for high volume trading, lightweight protocols for IoT. By combining theoretical limits with a range of practical issues such as state transfer and cryptographic overhead, we hope that the survey provides a structured roadmap for researchers tackling the scalability-security trade-offs in future distributed systems.