rich1.0npub1vjzmc45k8dgujppapp2ue20h3l9apnsntgv4c0ukncvv549q64gsz4x8ddhttps://nostr.ae/npub1vjzmc45k8dgujppapp2ue20h3l9apnsntgv4c0ukncvv549q64gsz4x8ddnjumphttps://nostr.ae📅 Original date posted:2022-11-21 📝 Original message: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20221120/2a736ba2/attachment.html>