{"type":"rich","version":"1.0","author_name":"npub1m230cem2yh3mtdzkg32qhj73uytgkyg5ylxsu083n3tpjnajxx4qqa2np2","author_url":"https://nostr.ae/npub1m230cem2yh3mtdzkg32qhj73uytgkyg5ylxsu083n3tpjnajxx4qqa2np2","provider_name":"njump","provider_url":"https://nostr.ae","html":"📅 Original date posted:2022-02-19\n📝 Original message:\nOn Fri, Feb 18, 2022 at 04:38:27PM -0800, Jeremy Rubin wrote:\n\u003e \u003e As I said, it's a new kind of pinning attack, distinct from other types\n\u003e of pinning attack.\n\u003e \n\u003e I think pinning is \"formally defined\" as sequences of transactions which\n\u003e prevent or make it less likely for you to make any progress (in terms of\n\u003e units of computation proceeding).\n\nMentioning \"computation\" when talking about transactions is misleading:\nblockchain transactions have nothing to do with computation.\n\n\u003e Something that only increases possibility to make progress cannot be\n\u003e pinning.\n\nIt is incorrect to say that all use-cases have the property that any version of\na transaction being mined is progress.\n\n\u003e If you want to call it something else, with a negative connotation, maybe\n\u003e call it \"necromancing\" (bringing back txns that would otherwise be\n\u003e feerate/fee irrational).\n\nNecromancing might be a reasonable name for attacks that work by getting an\nout-of-date version of a tx mined.\n\n\u003e In particular, for the use case you mentioned \"Eg a third party could mess\n\u003e up OpenTimestamps calendars at relatively low cost by delaying the mining\n\u003e of timestamp txs.\", this is incorrect. A third party can only accelerate\n\u003e the mining on the timestamp transactions, but they *can* accelerate the\n\u003e mining of any such timestamp transaction. If you have a single output chain\n\u003e that you're RBF'ing per block, then at most they can cause you to shift the\n\u003e calendar commits forward one block. But again, they cannot pin you. If you\n\u003e want to shift it back one block earlier, just offer a higher fee for the\n\u003e later RBF'd calendar. Thus the interference is limited by how much you wish\n\u003e to pay to guarantee your commitment is in this block as opposed to the next.\n\nYour understanding of how OpenTimestamps calendars work appears to be\nincorrect. There is no chain of unconfirmed transactions. Rather, OTS calendars\nuse RBF to _update_ the timestamp tx with a new merkle tip hash for to all\noutstanding per-second commitments once per new block. In high fee situations\nit's normal for there to be dozens of versions of that same tx, each with a\nslightly higher feerate.\n\nOTS calendars can handle any of those versions getting mined. But older\nversions getting mined wastes money, as the remaining commitments still need to\nget mined in a subsequent transaction. Those remaining commitments are also\ndelayed by the time it takes for the next tx to get mined.\n\nThere are many use-cases beyond OTS with this issue. For example, some entities\nuse \"in-place\" replacement for update low-time-preference settlement\ntransactions by adding new txouts and updating existing ones. Older versions of\nthose settlement transactions getting mined rather than the newer version\nwastes money and delays settlement for the exact same reason it does in OTS.\n\nIf fee accounts or any similar mechanism get implemented, they absolutely\nshould be opt-in. Obviously, using a currently non-standard nVersion bit is a\npossible approach. Conversely, with CPFP it may be desirable in the settlement\ncase to be able to *prevent* outputs from being spent in the same block. Again,\nan nVersion bit is a possible approach.\n\n\u003e By the way, you can already do out-of-band transaction fees to a very\n\u003e similar effect, google \"BTC transaction accelerator\". If the attack were at\n\u003e all valuable to perform, it could happen today.\n\nI just checked: all the BTC transaction accellerator services I could find look\nto be either scams, or very expensive. We need compelling reasons to make this\nnuisance attack significantly cheaper.\n\n\u003e Lastly, if you do get \"necromanced\" on an earlier RBF'd transaction by a\n\u003e third party for OTS, you should be relatively happy because it cost you\n\u003e less fees overall, since the undoing of your later RBF surely returned some\n\u003e satoshis to your wallet.\n\nAs I said above, no it doesn't.\n\n-- \nhttps://petertodd.org 'peter'[:-1]@petertodd.org\n-------------- next part --------------\nA non-text attachment was scrubbed...\nName: signature.asc\nType: application/pgp-signature\nSize: 833 bytes\nDesc: not available\nURL: \u003chttp://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20220219/e3194806/attachment-0001.sig\u003e"}