Optimal extension protocols for byzantine broadcast and agreement

The problems of Byzantine Broadcast (BB) and Byzantine Agreement (BA) are of interest to both the distributed computing and cryptography communities. Extension protocols for these primitives have been introduced to handle long messages efficiently at the cost of small number of single-bit broadcasts, referred to as seed broadcasts. While the communication optimality has remained the most sought-after property of an extension protocol in the literature, we prioritize both communication and round optimality in this work. In a setting with n parties and a static adversary controlling at most t parties in Byzantine fashion, we present BB and BA extension protocols with t更多