Abstract. A Blockchain system such as Ethereum is a peer to peer network where each node works in three phases: creation, mining, and vali- dation phases. In the creation phase, it executes a subset of locally cached transactions to form a new block. In the mining phase, the node solves a cryptographic puzzle (Proof of Work - PoW) on the block it forms. On receiving a block from another peer, it starts the validation phase, where it executes the transactions in the received block in order to ensure all transactions are valid. This execution also updates the blockchain state, which must be completed before creating the next block. A long block validation time lowers the system’s overall throughput and brings the well known Verifier’s dilemma into play. Additionally, this leads to wasted mining power utilization (MPU).
    Through extensive measurement of 2000 nodes from the produc- tion Ethereum network we find that during block validation, nodes redundantly execute more than 80% of the transactions in greater than 75% of the blocks they receive - this points to significant potential to save time and computation during block validation.
    Motivated by this, we present Renoir, a novel mechanism that caches state from transaction execution during the block creation phase and reuses it to enable nodes to skip (re)executing these trans- actions during block validation. Our detailed evaluation of Renoir on a 50 node testbed mimicking the top 50 Ethereum miners illus- trates that when gas limit is increased to 20 times the default value, to accommodate computationally intensive transactions, Renoir reduces validation time by 90% compared to Ethereum. In addi- tion, throughput of Ethereum reduces from 35326 tx/hour to 24716 tx/hour and MPU from 96% to 67% but these barely change for Renoir. Furthermore, we deploy a node running Renoir on the production Ethereum network. Our measurement illustrates that Renoir reduces the block validation time by as much as 50%

Paper

Abstract. Cryptocurrency networks are a promising infrastructure for pseudonymous online payments. However, low throughput has prevented their widespread acceptance. A promising solution to scale throughput is the Payment channel network (PCN), exemplified by the Lightning Network (LN), that uses a network of off-chain bidirectional payment channels between parties that wish to transact often. Since payments use the shortest paths with sufficient funds over this network, channel balances get exhausted in the direction transactions flow and eventually become unidirectional. This results in transactions failing and consequently a lower transaction success ratio. Our observations on the production LN show that over 63% of the channels lose over 80% of the channel balance in one direction over time, which makes the success ratio of a real-world workload drop from 71% to 29%. A unidirectional channel along a path results in a failure message back to the source that recomputes the path, excluding the failed channel and reattempts the transaction, thus adding to the completion latency even for those transactions that do complete.
    We propose REBAL, a distributed re-balancing mechanism, and a new routing scheme to address the above issues. REBAL maximizes the extent to which channels can be re-balanced across the entire network. REBAL addresses the completion latency issue by re-routing transactions from intermediate nodes around a unidirectional channel rather than propagating the failure back to the source.
    Our comprehensive evaluation of REBAL shows that the success ratio improves from 30.18% to 79.54% and success volume from 3.98% to 29.99% for a real-world workload derived from the Ripple network, without adversely impacting the transaction latency. Even at very high transaction rates, REBAL outperforms Lightning Network Daemon (LND- a Golang implementation of LN) (12%) with a success ratio of 43.76%.

Paper

Abstract. Unlike Renoir, Renoir-NG intent to reduce both block validation time as well as block creation time.