Anonymous Multi-Hop Locks for Blockchain Scalability and Interoperability

Abstract

Tremendous growth in cryptocurrency usage is exposing the inherent scalability issues with permissionless blockchain technology. Payment-channel networks (PCNs) have emerged as the most widely deployed solution to mitigate the scalability issues, allowing the bulk of payments between two users to be carried out off-chain. Unfortunately, as reported in the literature and further demonstrated in this paper, current PCNs do not provide meaningful security and privacy guarantees [30], [40]. In this work, we study and design secure and privacypreserving PCNs. We start with a security analysis of existing PCNs, reporting a new attack that applies to all major PCNs, including the Lightning Network, and allows an attacker to steal the fees from honest intermediaries in the same payment path. We then formally define anonymous multi-hop locks (AMHLs), a novel cryptographic primitive that serves as a cornerstone for the design of secure and privacy-preserving PCNs. We present several provably secure cryptographic instantiations that make AMHLs compatible with the vast majority of cryptocurrencies. In particular, we show that (linear) homomorphic one-way functions suffice to construct AMHLs for PCNs supporting a script language (e.g., Ethereum). We also propose a construction based on ECDSA signatures that does not require scripts, thus solving a prominent open problem in the field. AMHLs constitute a generic primitive whose usefulness goes beyond multi-hop payments in a single PCN and we show how to realize atomic swaps and interoperable PCNs from this primitive. Finally, our performance evaluation on a commodity machine finds that AMHL operations can be performed in less than 100 milliseconds and require less than 500 bytes of communication overhead, even in the worst case. In fact, after acknowledging our attack, the Lightning Network developers have implemented our ECDSA-based AMHLs into their PCN. This demonstrates the practicality of our approach and its impact on the security, privacy, interoperability, and scalability of today's cryptocurrencies.

Focus on Blockchain: A Comprehensive Survey on Academic and Application

“…At present, it seems that increasing the block size and Lightning Network are the only two mode options for expanding the Bitcoin system, but this is actually just the two mainstream methods currently favored by BCH and BTC [50]. In fact, there are many other suggestions for improving throughput, including sidechains, Blockchain [51] studied and designed a secure and private PCNS. Smart contract is a kind of automatic implementation protocol, and the scalability challenge hinders its further adoption.…”

Solutions to Scalability of Blockchain: A Survey

“…Payment channels have been widely researched in recent years, releasing several implementations of the Lightning Network [99]- [101]. Besides, there are many other solutions of off-chain payment channel from academia, including Bitcoin Duplex Micropayment Channels [26], Sprites [28], AMHLs [102]. Sprites develops constant locktimes to improve transaction throughput in Payment channel networks and support incremental deposits and withdrawals without interrupting the payment channel.…”

The Role of Blockchain Technology in Telehealth and Telemedicine

“…Thus, telehealth services can generate an enormous amount of data that requires fast data processing to obtain insights from the health data [65]. However, in the current blockchain platforms, the large amount of healthcare data affects transaction fees and total waiting time of a transaction to be confirmed [66,67]. The Ethereum platform can handle up to twenty transactions per second [68].…”