Fulgor & Rayo

Concurrency and Privacy with Payment-Channel Networks

We lay the foundations for privacy and concurrency in payment-channel networks (PCN), presenting a formal definition and two provably secure solutions: Fulgor and Rayo. Fulgor provides provable privacy guarantees for PCNs and is fully compatible with the Bitcoin scripting system. Rayo enforces non-blocking progress (i.e., at least one of the concurrent payments terminates). Interestingly, we show through a new impossibility result that non-blocking progress necessarily comes at the cost of weaker privacy. At the core of Fulgor and Rayo is Multi-Hop HTLC, a new smart contract, compatible with the Bitcoin scripting system. Our performance evaluation of Fulgor and Rayo demonstrates their feasibility to be deployed in practice. [Paper]


Efficient Decentralized Routing for Path-Based Transactions

At the core of a payment-channel network (PCN) is a routing algorithm that discovers transaction paths between sender and receiver. Existing routing algorithms lack either efficiency or privacy, as well as the comprehensive analysis that is indispensable to ensure the success of PCNs in practice. We have designed and evaluated SpeedyMurmurs, a novel routing algorithm for PCNs using efficient and flexible embedding-based path discovery and on-demand efficient stabilization to handle the dynamics of a PCN. Our simulation study, indicates that SpeedyMurmurs reduces the overhead of stabilization by up to two orders of magnitude and the overhead of routing a transaction by more than a factor of two. Finally, SpeedyMurmurs can be useful also in decentralized credit networks such as SilentWhispers and inter-blockchain protocols such as Interledger. [Paper]

External Collaborators