Hi Michael, Thanks for the feedback,
On the first point, I think it should be underscored how much this proposed credential system, while labeled a reputational one, belongs more to a monetary strategy (after the fact should be called "staking" credentials). Indeed, there is a direct link between the credentials and a cost expressed in satoshis. Therefore, in case of loopholes in the system damages are effectively borne by the routing hops, without throwing the whole system down. Note, the default policy should be some 0-risk HTLC forward acceptance. On the second point, we already have today's reputation systems in Lightning, namely the routing algorithms keeping track of the performance of the routing hops, and their liquidity. That information is used in a continuous fashion to improve payment-path building. And while those algorithms are doing probabilistic estimation of the balance distribution, the proposed credential system is not all relying on past statistics for its effectiveness (as long as the node operators are requiring credentials of worthiness equivalent to routing fees). On the third point, the protocol defer to the node operators all the decisions on the credential acquisition costs, expiration height, binding with liquidity units, or even allow additional routing policy checks. Flexibility is offered to the node operators, without the protocol developers trying to do any "centralized" decision on the cost of the credentials or whatever. >From my understanding, the critics you're raising, while potentially correct for the reputation systems links you're including, does not bind to any concrete point of my proposal. I hope you'll take time to browse the proposal as detailed more in depth here: https://github.com/lightning/bolts/pull/1043 Best, Antoine Le sam. 26 nov. 2022 à 05:53, Michael Folkson <michaelfolk...@protonmail.com> a écrit : > Hi Antoine > > I've got a lot to catch up on re channel jamming but just to say I'm > deeply skeptical about attempting to embed a reputation layer or reputation > credentials into the Lightning protocol. Admittedly I'm somewhat of a > curious amateur in the field of reputation systems but a number of people > (me included) have had to look into reputation systems in the past for > projects/startups they were working on and *centralized* reputation > systems are absolute minefields to manage effectively though some > corporations do manage it. Decentralized reputation systems baked into a > protocol is just a step too far. All you need is one edge case where the > attacker can ensure an innocent party is blamed and the reputation system > falls apart. The protocol developer is in the position of assessing who is > telling the truth out of two opposing viewpoints on Reddit etc. > > I do think reputation systems will play a key part in a future Lightning > Network (to some extent they already are with sites like 1ML and Amboss) > but they won't be managed by protocol devs, they will be managed by > multiple flavors of companies and projects (hopefully open source but most > likely closed source too, for profit, non-profit etc) who are free to use > whatever metrics and weigh those metrics however they like. The protocol > just can't afford to expand into areas where there is case by case judgment > and statistical analysis required. It will become bloated, ineffective and > put protocol developers in the position of deciding who ultimately receives > routing fees rather than just enabling payments can get from A to B. > Identity is easier, you either control a private key or you don't. > Reputation is much more difficult, there will be some attacks where a > probabilistic assessment will need to be made on who the perpetrator of the > attack was. You don't add that to the (already long) list of protocol > developers' responsibilities. > > So feel free to continue to explore reputation and reputation systems but > a strong warning that this is likely not solved at the protocol level. > Decisions protocol developers make will impact what data can be collected > and how easy that data is to collect (there are already some tricky > trade-offs with regards to privacy, routing success and transparency for > when things go wrong) but beyond that protocol developers should leave it > to others. I've included some links to some additional reading on > reputation systems in case you are interested. > > Thanks > Michael > > [0]: > https://www.amazon.com/Building-Reputation-Systems-Randy-Farmer/dp/059615979X/ > [1]: > https://medium.com/openbazaarproject/decentralized-reputation-in-openbazaar-1a577fac5175 > [2]: https://www.bitrated.com/faq > > -- > Michael Folkson > Email: michaelfolkson at protonmail.com > Keybase: michaelfolkson > PGP: 43ED C999 9F85 1D40 EAF4 9835 92D6 0159 214C FEE3 > > ------- Original Message ------- > On Monday, November 21st, 2022 at 06:01, Antoine Riard < > antoine.ri...@gmail.com> wrote: > > Hi LN Devs, > > tl;dr A formalization of a reputation-based scheme to solve channel > jamming is proposed. The system relies on "credentials" issued by routing > hops and requested to be attached to each HTLC forward request. The > "credentials" can be used by a reputation algorithm to reward/punish > payment senders and allocate channel liquidity resources efficiently. The > "credentials" initial distribution can be bootstrapped leveraging one-time > upfront fees paid toward the routing hops. Afterwards, the "credentials" > subsequent distribution can rely on previous HTLC traffic. > > A protocol description can be found here, with few extensions already to > the BOLTs: > > https://github.com/lightning/bolts/pull/1043 > > There is also a work-in-progress proof-of-concept in LDK (on top of our > coming soon^TM HTLC intercepting API): > > https://github.com/lightningdevkit/rust-lightning/pull/1848 > > This work builds on previous reputation-scheme research [0] [1]. It also > integrates the more recent proposals of upfront fees as a straightforward > mechanism to bootstrap the reputation system. Bootstrapping the system with > more economically cost-effective privacy-preserving UTXO ownership proofs > not only add another layer of engineering complexity, there is still a > proof size vs proof generation/validation trade-off to arbiter between ZKP > cryptosystems. > > Rather to seek for a game-theory equilibrium defined as a breakeven point > as in the latest unconditional fee research [2], this proposal aims to use > reputation credentials to allow HTLC traffic-shaping. This not only should > protect against jamming situations (either malicious > or spontaneous) but also allow active HTLC traffic-shaping, where a > routing hop can allow extended channel liquidity lockups based on > accumulated reputation (e.g for hold-invoices). This is also a reduced > overhead cost, as upfront fees are only paid at bootstrap, or when the HTLC > forward behavior can be qualified as "whitewashing" from the routing hop > viewpoint. > > It should be noted, this current reputation-credential architectural > framework assumes credentials distribution at the endpoint of the network. > However, the framework should be flexible enough for the credentials to be > harvested by the LSPs, and then distributed in a secondary fashion to their > spokes, when they need it, or even attached transparently thanks to > trampoline. So one design intuition, there is no strong attachment of the > reputation to the endpoint HTLC sender, even if the protocol is described > in a "flat" view for now. > > Let's evaluate quickly this mitigation proposal against a few criterias > emerged from recent research. > > The mitigation is effective, in the sense a routing hop can apply a > proportional relationship between the acquisition of the reputation and the > amount of liquidity resources credited in function of said reputation. In a > period of steady state, the reputation acquisition cost can be downgraded > to 0. In periods of channel congestion, the reputation credentials to > liquidity units translation can be severed, in the limit of routing hop > acceptable competitiveness. > > The mitigation is incentive-compatible, if the credentials are not honored > by their issuers, the HTLC senders can evict them from the routing network > view for a while. The successful usage of credentials can lead to more > credentials allocated for longer and more capacity-intensive channel > lockups. In case of HTLC failure, the failure source could be forgiven by > routing hops to maintain the worthiness of the sender credentials. > > The mitigation can be made transparent from the user, as the credentials > harvesting can be done automatically from a pre-allocated budget, similar > to the fee-bumping reserves requirement introduced by anchor output. At the > end of today, if we take modern browsers as an example, the average user > doesn't check manually the TLS certificates (for what they're worth...). > > The mitigation can conserve high-level privacy, as the usage of blinded > signature (or another equivalent cryptosystem breaking signature/message > linking) should allow the credentials issued during a preliminary phase to > be undistinguishable during the redeem/usage phase. New CPU/memory DoS > vectors due to the credentials processing should be watched out. > > About the ease of implementation, there are few protocol messages to > modify, a HTLC intercepting API is assumed as supported by the > implementation, onion messages support is also implied, landing EC blinded > signature in libsecp256k1-zkp shouldn't be a big deal, routing algorithms > adaptations might be more serious but still reasonable. The > "credentials-to-liquidity" allocation algorithms are likely the new real > beast, though I don't think any reputation scheme can spare them. > > There could be a concern about the centralization inertia introduced by a > reputation system. Intuitively, the argument can be made that any > historical tracking (such as routing buckets) favor established LN > incumbents at the gain of efficiency. A counter-argument can be made, a new > routing hop can lower the acquisition cost of its issued credentials to > attract more HTLC traffic (accepting higher jamming risk). > > On the ecosystem impacts, it should be studied that this proposal would > impact things like inbound channel routing fees [3], ratecard [4] or > flow-control valve [5] and the whole liquidity toolchain. Hopefully, we > don't significantly restrain the design space for future LN protocol > upgrades. > > On the proposal modularity and flexibility, each routing node has > oversight on its routing policy, acquisition methods, credentials to > liquidity rate. New acquisition methods can be experimented or deployed > when ready, e.g stakes certificates with only e2e upgrade. The credentials > themselves could have "innate" expiration time if we use things like > short-lived ZKP [6]. The credentials framework can be extended beyond > solving jamming, as a generalized risk-management framework for Bitcoin > decentralized financial network, e.g transaction signature exchange > ordering in multi-party transactions [7] or finding reliable Coinjoin > counterparties. > > Feedback welcome. > > Cheers, > Antoine > > [0] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-November/002884.html > [1] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-August/003673.html > [2] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-November/003740.html > [3] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-July/003643.html > [4] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-September/003685.html > [5] > https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-September/003686.html > [6] https://eprint.iacr.org/2022/190.pdf > [7] https://github.com/lightning/bolts/pull/851#issuecomment-1290727242 > > >
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