A Formally Veriied Algorithm for Interactive Consistency under a Hybrid Fault Model

Thambidurai and Park 13] have proposed an algorithm for Interactive Consistency that retains resilience to the arbitrary (or Byzantine) fault mode, while tolerating more faults of simpler kinds than standard Byzantine-resilent algorithms. Unfortunately, and despite a published proof of correctness, their algorithm is awed. We detected this while undertaking a formal veriication of the algorithm. We present a corrected algorithm that has been subjected to mechanically-checked formal veriication. Because informal proofs seem unreliable in this domain, and the consequences of failure could be catastrophic , we believe formal veriication should become standard for algorithms intended for safety-critical applications.