## Cryptology ePrint Archive: Report 2020/166

Ethna: Channel Network with Dynamic Internal Payment Splitting

Stefan Dziembowski and Paweł Kędzior

Abstract: \emph{Off-chain channel networks} are one of the most promising technologies for dealing with blockchain scalability and delayed finality issues. Parties that are connected within such networks can send coins to each other without interacting with the blockchain. Moreover, these payments can be routed'' over the network. Thanks to this, even the parties that do not have a channel in common can perform payments between each other with a help of intermediaries.

In this paper, we present a new technique (that we call \emph{Dynamic Internal Payment Splitting (DIPS)}) that allows the intermediaries in the network to split the payments into several sub-payments. This can be done recursively multiple times by subsequent intermediaries. Moreover, the resulting payment receipts'' can be aggregated by each intermediary into one short receipt that can be propagated back in the network. We present a protocol (that we call Ethna'') that uses this technique. We provide a formal security definition of our protocol and we prove that Ethna satisfies it. We also implement a simple variant of Ethna in Solidity and provide some benchmarks.

Category / Keywords: cryptographic protocols / blockchain, smart contracts, payment networks