This tripwire idea is interesting. Basically "canary in consensus". I agree it's valuable. In the scenario of adversarial actor(s) gaining access to CQRC first, i.e. no whitehats, only blackhats, obviously nothing to discuss; touching a NUMS ECDL is the last thing they'll do. So I'm slightly worried that the general userbase will not notice that point, instead thinking it's a solid defense when it ... depends. In the scenario of at least some whitehats, we get wires tripped, or canaries singing. Having it in consensus is nice. The blockchain then does its job of being an unambiguous signal and we can have all the arguments well ahead of time. [1] On the other hand, we traditionally design such systems adversarially, right, so you could argue that an overfocus on this might be suboptimal - it might be better to do other things. (Similar comment applies to the 'smaller group canary' - definitely nothing wrong with it, but it is not in itself a defence unless we strongly believe whitehats, and *active* whitehats at that, are keeping up). An obvious question to raise: would we consider tripwiring a 192 bit group break of a similar type (NUMS)? I find that ... plausible? > The BIP341 NUMS point (which I suggest using in this context) is the point whose X coordinate is the SHA256 hash of the generator point G. This guarantees that the NUMS point cannot predate G (if it did, it would be possible in theory that secp256k1's designers actually chose G in function of what we call that NUMS point, giving it a DLP known to them). w.r.t. 'This guarantees that the NUMS point cannot predate G' yes based on SHA2 preimage resistance, but: isn't the real point that we're relying on SHA-2 not being a naughty function so that you couldn't find G = a * B and SHA2(G) = b*B for some base B in some feasible computation (sans CQRC of course, as was likely back then!). I have no idea what precise name you give to that property. OK, this is a ridiculous thing to discuss, perhaps, given when SHA2 and secp256k1 were standardized :) And given the encoding choices for our BIP341 NUMS (iirc the same as for Elements back in the day? using uncompressed encoding?) were able to be counted on the fingers of the hand which the sleeve does not cover :) [1] I take Antoine's point that making it consensus means the miners are involved and there is a non-trivial collusion risk if the stakes are high, but I can't see how this scenario is *worse* than no tripwire? On Sunday, July 5, 2026 at 4:07:33 PM UTC-6 Antoine Riard wrote: > Hi Pieter, > > Thanks for the observations. > > When I was saying there is a problem with the game theory, > it's that strikingly, any activation of the tripwire logic > would rely on a "flag" transaction being mined in the chain > for the network nodes starting to enforce at the block N or > N+1 or whatever the EC disabling threshold. > > Any "flag" transaction can be itself re-orged out of the chain > to purely disable the effects of the EC disabling threshold, > therefore make it null and void as an effect. One might see > it as a competing race between a group of "sunsetting" users > and a (majority) coalition of miners in coordination with a > CRQC adversary, where the latter have an interest and the > hashrate capabilities to do a tx-withold [0]. > > In pure terms of satoshi fee denominated calculus, empirically > global miners have won an average of $20 B yearly. If we only > consider that P2PK are going to be frozen by the tripwire effect, > as for most of them it might be assumed they will never move to > a safer format, we talk already about 1.7 M of coins or as of > today valuation $107 B (the information is on the chain and can > be verified). > > That's $107B can "burn" in revenue or income that a CRQC-enabled > miners coalition to constantly reorg-out the "flag" tx out of the > chain. In other terms, something like 5 years of income, and I > kindly do not count all the loss coins that are likely to amount > to a far bigger "tripwire" neutralization budget. > > In the name of what a majority of miners will gracefully let on > the table an opportunity of massive income ? > > Leveraging Shor the exploitation might be even done anonymously > as the mining process is done. Not even certainty, by who the > EC-protected coins could be covertly exfiltrated. > > That's the most striking problem when you think about the math > with any "tripwire" approach, or even an "hourglass" one relying > on a "flag" transaction [1]. I'm ruling out "checkpoints" and > any other trust-the-dev approach, as that's even worst [2]. > > As you're introducing post is resounding, what the miners > are saying now, there are no guarantees on how they would use > their hashrate down the road, potentially 10 or 20 years from now. > > Beyond, and to answer back your point, I still think you can > manage an escape hatch of the "tripwire" effect, it's all depends > how the script tripwire logic is implemented, but if you have > two OP_SUCCESS of different kinds before your EC CHECKSIG, you > can always have a "soft-fork" after the "tripwire" to return > true on the stack, with an EC or hashlock as a success (I agree > using undefined op_success in a script is not safe at all) [3]. > > Best, > Antoine > OTS hash: 4bc91d8dee1625f6e78b27c88bced8e405f25ef6d3d8fd59be8016db5b0fbe66 > > [0] See naumenkog's https://www.bitmex.com/blog/txwithhold-smart-contracts > [1] This is sad, as the "hourglass" depending how the parameters are chosen > was a more acceptable trade-off than pure sunsetting. > [2] Given the amounts at stake to sunset, as a group of developers you > would just paint yourself a target, there are more even funds at stake > that Satoshi herself / himself is assumed to have. > [3] There is no security proof in BIP341 on the unforgeability of the > NUMS point, if it binds in the ROM or whatever. > > Le sam. 4 juil. 2026 à 13:47, Sjors Provoost a > écrit : > >> >> >> On Fri, Jul 3, 2026, at 23:23, Pieter Wuille wrote: >> >> [...] >> >> > * Just publishing the DLP in a transaction (e.g. OP_RETURN with a >> > specific marker). This is smaller than a full transaction input + >> > signature. >> > >> > * Similarly, but publishing in the coinbase, and requiring relay using >> > a separate message. Less places a node needs to check, but I'm >> > concerned about the difficulty of testing infrastructure that relay of >> > such a message works >> >> [...] >> >> > >> > On Saturday, June 27th, 2026 at 12:33 AM, Anthony Towns >> > wrote: >> > >> >> A slight variant of this approach would be to have a 128 byte value >> "aRsm", such that P = N+a*G, N is the BIP-341 NUMS point, and Rs is a >> BIP340 signature of m by P. That would allow the victim of post-quantum >> theft via a key-path spend of a BIP341 NUMS IPK to trigger the tripwire, in >> addition to someone who has direct access to a CRQC. >> > >> > Indeed, I had considered something similar, but see above for why I'm >> > not convinced supporting non-cooperative CRQCs is that useful. >> > >> > Also, in my view the tripwire isn't really a security feature on itself >> > (it's not expected to trigger...), but more something that sets >> > expectations around the output type for prospective users. >> > >> > In that sense, the question is really whether supporting >> > non-cooperative CRQCs helps set that expectation more than only >> > cooperative ones, which are definitely easier to support. >> > >> >> I think it could make sense to have the tripwire be included in the >> block via the coinbase witness commitment output, rather than having it be >> locked to a transaction, so you only having to check the coinbase for the >> magic rather than every transaction. That would require a separate P2P >> message to relay the necessary ECDL-break proof to miners, and would >> probably need stratumv2 or a getblocktemplate update in order for the node >> to be able to tell pools to actually include that info in the coinbase. >> > >> > I worry this is untestable, really. You'd need things like >> > fake-tripwires to be supported through the same message which don't >> > require an ECDLP break, and still propagate. And then that needs DoS >> > protection measures, >> >> I whipped something up last weekend: >> https://github.com/Sjors/bitcoin/pull/121 >> >> It seems straightforward, but maybe I missed something: >> - for test code we use a fake NUMS point, so we can generate "proof" >> without a quantum computer >> - a p2p message floods the proof >> - nodes ignore the message if they already have *any* valid proof >> - verifying p2p proof candidates might need some rate limiting, but it's >> as cheap as verifying a transaction signature >> - mining code includes the proof in a coinbase op_return, until the >> freeze activates >> - with stratum v2 (and ipc mining clients in general this works out of >> the box, a small change is needed for getblocktemplate clients) >> - since the proof is not in the header, we can't use the normal bip9 >> style header scan to see if the rule activated. Instead the prototype >> stores it in a file along with a merkle inclusion proof, which is read when >> the node restarts. >> >> With this mechanism it doesn't really need to be in the coinbase >> transaction, but that does seem more convenient and miners can censor it >> anyway. >> >> - Sjors >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "Bitcoin Development Mailing List" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/bitcoindev/aWYtPLVPZ3U/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> bitcoindev+...@googlegroups.com. >> To view this discussion visit >> https://groups.google.com/d/msgid/bitcoindev/002f2395-7d5d-4cb6-852c-e991aa1f0eb3%40app.fastmail.com >> . >> > -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. 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