Authors:
Utz Nisslmueller
1
;
Klaus-Tycho Foerster
1
;
Stefan Schmid
1
and
Christian Decker
2
Affiliations:
1
Faculty of Computer Science, University of Vienna, Vienna, Austria
;
2
Blockstream, Zurich, Switzerland
Keyword(s):
Cryptocurrencies, Bitcoin, Payment Channel Networks, Routing, Privacy
Abstract:
Cryptocurrency off-chain networks such as Lightning (e.g., Bitcoin) or Raiden (e.g., Ethereum) aim to increase the scalability of traditional on-chain transactions. To support nodes to learn about possible paths to route their transactions, these networks need to provide gossip and probing mechanisms. This paper explores whether these mechanisms may be exploited to infer sensitive information about the flow of transactions, and eventually harm privacy. In particular, we identify two threats, related to an active and a passive adversary. The first is a probing attack: here the adversary aims the maximum amount which is transferable in a given direction of a target channel, by active probing. The second is a timing attack: the adversary discovers how close the destination of a routed payment actually is, by acting as a passive man-in-the middle. We then analyze the limitations of these attacks and propose remediations for scenarios in which they are able to produce accurate results.