CLoTH: A Lightning Network Simulator

3noPayment-channel networks are one of the most promising solution to the well-known issue of blockchain scalability. In this work we present CLoTH, a simulator of the Lightning Network — the mainstream payment-channel network, used in Bitcoin. CLoTH simulates the execution of payments in a payment-channel network and produces performance measures such as the probability of payment success and the average payment time. To the best of our knowledge, CLoTH is the only simulator that faithfully reproduces the Lightning Network code functions, and this ensures the reliability of simulation results. In this work we provide a detailed description of the new, refactored, publicly-usable version of CLoTH, and we show simulations on the multi-path-payment feature, a recent Lightning Network feature that aims to minimize payment failures.openopenConoscenti, Marco; Vetrò, Antonio; De Martin, Juan CarlosConoscenti, Marco; Vetrò, Antonio; De Martin, Juan Carlo

Boomerang: Redundancy Improves Latency and Throughput in Payment-Channel Networks

In multi-path routing schemes for payment-channel networks, Alice transfers funds to Bob by splitting them into partial payments and routing them along multiple paths. Undisclosed channel balances and mismatched transaction fees cause delays and failures on some payment paths. For atomic transfer schemes, these straggling paths stall the whole transfer. We show that the latency of transfers reduces when redundant payment paths are added. This frees up liquidity in payment channels and hence increases the throughput of the network. We devise Boomerang, a generic technique to be used on top of multi-path routing schemes to construct redundant payment paths free of counterparty risk. In our experiments, applying Boomerang to a baseline routing scheme leads to 40% latency reduction and 2x throughput increase. We build on ideas from publicly verifiable secret sharing, such that Alice learns a secret of Bob iff Bob overdraws funds from the redundant paths. Funds are forwarded using Boomerang contracts, which allow Alice to revert the transfer iff she has learned Bob's secret. We implement the Boomerang contract in Bitcoin Script

On the (Not So) Surprising Impact of Multi-Path Payments on Performance and Privacy in the Lightning Network

The Lightning network (LN) addresses Bitcoin’s scalability issues by providing fast and private payment processing. In order to mitigate failures caused by insufficient channel capacities, LN introduced multi-path payments. To the best of our knowledge, the effect of multi-path payments remains unclear. In this paper, we therefore study the impact of multi-path payments on performance and privacy. We identify metrics quantifying the aforementioned properties and utilise them to evaluate the impact of multi-path payments. To this end, we develop a simulator implementing pathfinding in LN using single and multi-path payments as well as various pathfinding algorithms. We find that, while the success rate of multi-path payments is up to 20% higher, the impact of multi-path payments on performance otherwise remains within limits. On the other hand, the impact on privacy appears to be greater, e.g., multi-path payments are more likely to encounter an on-path adversary and the relationship anonymity is more likely to be compromised by colluding intermediate hops. However, multi-path payments are less likely to be deanonymised based on the path lengths

Payment Splitting in Lightning Network as a Mitigation Against Balance Discovery Attacks

Bitcoin has a low throughput of around 7 transactions per second. The Lightning Network (LN) is a solution meant to improve that throughput while also improving privacy. LN is a Payment Channel Network (PCN) that runs as a peer-to-peer network on top of Bitcoin and improves scalability by keeping most transactions off-chain without sacrificing the trustless character of Bitcoin. Prior work showed that LN is susceptible to the Balance Discovery Attack that allows for individual channel balances to be revealed, threatening users\u27 privacy. In this work we introduce Payment Splitting and Switching (PSS), a way of splitting up payments in LN at intermediary hops along the payment path. PSS drastically reduces the information an attacker can obtain through a BDA. Using real-world data in an LN simulator we demonstrate that the information gain for the attacker drops up to 62% when PSS is deployed. Apart from its potential as mitigation against BDA, PSS also shows promise for increased LN throughput and as a mitigation against jamming attacks

Capabilities and Limitations of Payment Channel Networks for Blockchain Scalability

L'abstract è presente nell'allegato / the abstract is in the attachmen

SoK: Layer-Two Blockchain Protocols

Blockchains have the potential to revolutionize markets and services. However, they currently exhibit high latencies and fail to handle transaction loads comparable to those managed by traditional financial systems. Layer-two protocols, built on top of layer-one blockchains, avoid disseminating every transaction to the whole network by exchanging authenticated transactions off-chain. Instead, they utilize the expensive and low-rate blockchain only as a recourse for disputes. The promise of layer-two protocols is to complete off-chain transactions in sub-seconds rather than minutes or hours while retaining asset security, reducing fees and allowing blockchains to scale. We systematize the evolution of layer-two protocols over the period from the inception of cryptocurrencies in 2009 until today, structuring the multifaceted body of research on layer-two transactions. Categorizing the research into payment and state channels, commit-chains and protocols for refereed delegation, we provide a comparison of the protocols and their properties. We provide a systematization of the associated synchronization and routing protocols along with their privacy and security aspects. This Systematization of Knowledge (SoK) clears the layer-two fog, highlights the potential of layer-two solutions and identifies their unsolved challenges, indicating propitious avenues of future work

Non Atomic Payment Splitting in Channel Networks

Off-chain channel networks} are one of the most promising technologies for dealing with blockchain scalability and delayed finality issues. Parties connected within such networks can send coins to each other without interacting with the blockchain. Moreover, these payments can be ``routed\u27\u27 over the network. Thanks to this, even the parties that do not have a channel in common can perform payments between each other with the help of intermediaries. In this paper, we introduce a new notion that we call ``Non-Atomic Payment Splitting (NAPS)\u27\u27 protocols that allow the intermediaries in the network to split the payments recursively into several subpayments in such a way that the payment can be successful ``partially\u27\u27 (i.e.~not all the requested amount may be transferred). This contrasts with the existing splitting techniques that are ``atomic\u27\u27 in that they did not allow such partial payments (we compare the ``atomic\u27\u27 and ``non-atomic\u27\u27 approaches in the paper). We define NAPS formally and then present a protocol that we call ``EthNA\u27\u27, that satisfies this definition. EthNA is based on very simple and efficient cryptographic tools; in particular, it does not use expensive cryptographic primitives. We implement a simple variant of EthNA in Solidity and provide some benchmarks. We also report on some experiments with routing using EthNA