By Bitcoin Aldizkaria - Duela 6 hilabete - Irakurketa Denbora: 5 minutu
Ordainketa zatitzea eta aldatzea: pribatutasuna hobetzea eta ordainketaren arrakasta aldi berean
One of the fundamental limitations of the Lightning protocol is how payment routing is handled and accomplished. It is entirely source routed, meaning that the sender of a payment is the one who constructs the entire route from themselves to the receiver in order to facilitate the payment. This presents an issue when it comes to the changing balances of channels over time as they are routing payments between numerous different users across the network, once a sender "locks in" and decides on a specific route, that route cannot be changed until a failure message makes it way back to the sender, allowing them to construct an entirely new route going around the point where the initial attempt failed.
Honek UX astun eta gogaikarri bati aurre egin behar dio, edo ordainketa-zundaketa erabiltzea, nahita huts egingo dituzun ordainketak nahita lantzea, erabili nahi duzun ibilbideak funtzionatuko duen ikusteko, berriro saiatu aurretik benetako ordainketarekin. Lehenengoa erabiltzailearen esperientzia txarra besterik ez da eta ez nahi duzuna eskalarako pertsonentzako ordainketa-irtenbide bideragarria izan dadin zerbait landu nahi duzunean, eta bigarrenak neurrigabeko zama eragiten du sare osoan, bideratze-nodoek sareari aurre egin behar diotelako. Trafiko eta likidezia konplikazioak etengabeko ordainketen amaierako asmorik gabe ibilbide baten bideragarritasuna probatzeko.
Arazo hauen azken kausa bide batek ordainketa erdia aldatzeko ezintasuna da igorlearen inplikaziorik gabe. Ordainketa-bide osoa tipula enkriptatuta dagoenez, ezinezkoa da hori egitea. Salto bakoitzak aurretik duen saltoaren berri baino ez du ezagutzen, eta, ondoren, azken helmugaren ezagutzarik ez dute haietatik hargailura bitarteko bide alternatibo bat eraikitzeko.
Now, while this does present a huge barrier to shifting away from source-based routing, it doesn't entirely prevent it. As an intermediary node, while you can't completely reconstruct a new route from you to the destination, you can reroute the payment from yourself to the next hop defined in the path picked by the sender. So if Bob receives a payment that he is supposed to route to Carol, and the channel he is supposed to route it through doesn't have the capacity needed to forward it, he can send what he can through that channel and route the rest of the payment amount through other routes he can find from himself to Carol.
Last month Gijs van Dam wrote a proof of concept plugin for CLN (eskuragarri hemen) that does exactly that, building on multi-path payments that allow a payment to split up and take multiple routes to the receiver. If Bob and Carol are both running the plugin they can, in the appropriate situations, communicate to each other that a payment being forwarded along one channel is actually being partially rerouted so that Carol doesn't immediately drop it when she sees what she is being sent is less than what she is expected to forward. This way if alternate routes are available between Bob and Carol when the sender-decided route isn't viable, they can simply reroute the needed amount and the payment can succeed without having to completely fail, propagate back to the sender, and be rerouted by them.
If widely adopted as a standardized behavior on the network this could have a huge positive impact in the success rate of payments, drastically improving the UX of Lightning users looking for a simple payment mechanism that just works. It's an incredibly simple and logical behavior that could significantly improve a well known shortcoming. That's not all it can do though.
One of the big reasons that Gijs van Dam became interested in addressing this issue actually has nothing to do with simply improving the payment success rate and UX for users, it was actually because of a privacy shortcoming. One of the well known privacy issues that Lightning is vulnerable to is channel probing, this is the problem Gijs was concerned with.
Gorago aipatu dudan bezala, diru-zorro batzuek benetako ordainketa egin aurretik ordainketa arrakastatsua izango dela ziurtatzeko erabiltzen dute, baina teknika hau kanal baten bi aldeetan funtsen banaketa egiaztatzeko ere erabil daiteke. Behin eta berriz eta kontu handiz aukeratutako zenbatekoekin, zundaketa saiakera bakoitzaren arrakastak eta porrotak ondorioztatu dezakete funtsak kanalaren alde bakoitzean nola banatzen diren. Are gehiago hartu eta sistematikoki kanal ugaritan aldian-aldian eginda, teknika honek ordainketak desanonimizatu ere egin ditzake denbora errealean modu eraginkorrean ikusiz saldoak kanaletan aldatzen diren bitartean.
Tximista erabilera transakzionalerako pribatutasun-tresna gisa planteatzen da etengabe, baina errealitatea kanalak pribatutasuna aztertzea bezalako teknikak ematen dira, kasu askotan, onenean ere ahulak izan daitezke erabiltzaileak sarearekin nola elkarreragiten duen sofistikatua izan gabe. Ordainketa zatitzearen eta aldatzearen albo-ondorio interesgarrietako bat zundaketa erasoak ahultzen dituela da. Zundaketa-eraso batek funtzionatzen duen arrazoia zenbateko ezberdinekin probatzen jarraitu dezakezulako ordainketak huts egin arte. Ondo egiten bada, honek azken ordainketa saiakera arrakastatsuaren eta kanalaren saldoaren banaketa den porrotaren arteko tarte txikia ematen dizu.
In a world where Lightning nodes can on the fly reroute parts payments that would otherwise fail so they succeed, it completely breaks the inherent assumption that channel balance probing relies on. That your payment attempt will fail when the specific channel you decided to route through doesn't have the liquidity to forward it. With payment splitting and switching that assumption is no longer true, and the more nodes on the network support switching the more error prone it makes that assumption (by up to 62% according to a simulation using real-world Lightning network data by Gijs).
So not only is this proposal relatively simple, not only does it provide a path to improving the success rate of payment attempts, it also helps address one of the largest privacy shortcomings of the Lightning Network. I think especially in the wake of the recent Lightning vulnerability, this proposal shows that while Lightning is not without its share of problems, they are not impossible to solve or mitigate. It will even be very common for solutions to one problem to help with another problem.
Rome wasn't built in a day, and solutions that actually preserve Bitcoin's core properties in a scalable and sustainable way won't be either.
Jatorrizko iturria: Bitcoin Aldizkaria