ACCEL: Accelerating the Bitcoin Blockchain for High-throughput, Low-latency Applications

The Bitcoin blockchain is a secure, distributed ledger that enables trusted transactions across untrusted entities. However, many applications need much faster transaction confirmation than that of the current Bitcoin blockchain. In this paper, we present a high-throughput, low-latency, deterministic confirmation mechanism called ACCEL for accelerating Bitcoin's block confirmation mechanism. Our key idea for achieving faster confirmation is the quick identification of singular blocks that provably belong to the blockchain. While it is impossible to determine with certainty if a block belongs to a blockchain when network delays are unbounded, singular block detection exploits the fact that the end-to-end latency between Bitcoin miners is substantially lower than the inter-block spacing and can be assumed to be upper bounded. ACCEL is especially suitable for low-latency, permissioned blockchains, where the block spacing can be optimized to the blockchain's small latencies to greatly improve throughput. We evaluate ACCEL's performance with extensive simulations and with a real implementation built with minimal changes to and fully compatible with the Bitcoin blockchain. We show that with appropriate bounds on the end-to-end latency, it is possible to reduce transaction confirmation latencies to milliseconds with ACCEL, and so meet the performance needs of a wide range of applications.