Communication Optimal Multi-valued Asynchronous Broadcast Protocol

Broadcast (BC) is considered as the most fundamental primitive for fault-tolerant distributed computing and cryptographic protocols. An important and practical variant of BC is Asynchronous BC (known as A-cast). An A-cast protocol enables a specific party called sender (possibly corrupted) to send some message identically to a set of parties despite the presence of an adversary who may corrupt some of the parties in a malicious manner. Though the existing protocol for A-cast is designed for a single bit message, in real life applications typically A-cast is invoked on long message (whose size can be in gigabytes) rather than on single bit. Therefore, it is important to design efficient multi-valued A-cast protocols (i.e protocols with long message) which extract several advantages offered by directly dealing with long messages and are far better than multiple invocations to existing protocols for single bit. In this paper, we design highly efficient, communication optimal, optimally resilient multi-valued A-cast protocol for long messages, based on access to the existing A-cast protocol for short messages. Our protocol also provides better communication complexity than existing protocol for A-cast.