Hi Antoine,

> it would make any soft fork impossible.

This is probably tangential to the topic of the thread, but since you bring up the confiscatory potential of soft forks in general I will go ahead and plant my flag here by saying that if given the choice between doing a soft fork but with a high likelihood of freezing coins, or doing a hard fork to avoid freezing coins, I would pick the hard fork every time.

> As long as soft forks are tolerated, a degree of nuance needs to be
> introduced to take into account reasonable expectations from users

I believe what I wrote accounts for this nuance. As far as I'm aware, no soft fork ever intentionally froze coins; on the contrary, my observation has been that protocol developers are exceedingly cautious to avoid this side effect.[1] It appears their efforts have not been in vain, since broad confidence in the security of bitcoin property rights remains intact, as evidenced by the millions of people who continue to use bitcoin to store value.

> and incompatible with many soft fork proposal, including your own.

I'm not sure what you're referencing here; I am not an author of any soft fork proposals.

[1] Apparently the P2SH soft fork did freeze a total of 0.044 BTC: https://bitcoin.stackexchange.com/a/115804
This seems unintentional since the coins were created after the activation client was published and shortly before the fork activated, and I could not find any record of alarms being raised at the time about the prospect of freezing these coins.

On Fri, Feb 13, 2026, at 5:52 PM, Antoine Poinsot wrote:
> Hi John,
>
> Without commenting on the (un)desirability of freezing vulnerable coins
> (i largely share your
> concerns, but haven't yet formed an opinion of my own), i would like to
> surface one issue in part of
> your reasoning.
>
> You state:
>> A perhaps even more fundamental "collective assumption" of bitcoin users is that "a redeem script
>> that was valid at the time that a UTXO was encumbered will always remain valid". This is
>> fundamental to bitcoin's nature as p2p electronic cash. If users woke up one day no longer able to
>> assume that their redeem scripts would remain valid, then they would not be able to rely on
>> bitcoin to store value over time and the system would quickly collapse. Thus, any proposal to
>> disable features in a way that freezes coins is a proposal to destroy bitcoin.
>
> That's quite the sweeping claim, but it's trivially incorrect, or it
> would make any soft fork
> impossible. This is both disproven historically, since Bitcoin made
> previously-valid redeem scripts
> invalid on at least 5 occasions (post Satoshi), and incompatible with
> many soft fork proposal,
> including your own.
>
> As long as soft forks are tolerated, a degree of nuance needs to be
> introduced to take into account
> reasonable expectations from users, and not disabling
> potentially-vulnerable EC opcodes as opposed
> to upgrade hooks needs to be defended on its own merit rather than
> appealing to the destruction of
> Bitcoin. (And to be clear i think a strong case can be made in this
> regard, this is not to be
> interpreted as an argument in favour of The Big Freeze.)
>
> Best,
> Antoine
>
>
> On Friday, February 13th, 2026 at 5:13 PM, Light <bitcoin-dev@lightco.in> wrote:
>
>> Hi Pieter,
>>
>> > A small note aside: you can argue that it is possible for people to
>> > store coins insecurely, like in an OP_TRUE script output, or with
>> > private keys that are made public. I don't think this possibility
>> > affects the point above, because it is not about what possibilities
>> > exist, but which approaches people are likely to / asked to adopt.
>> > Nobody is incentivized or encouraged to store coins in an OP_TRUE.
>>
>> While it is true that "nobody is incentivized or encouraged to store coins in an OP_TRUE", I believe your argument is incomplete because it is missing a more realistic mass-theft vector, which is that as of today approximately 2.5 million BTC is held by less than two dozen centralized custodians.[1] These coins are at a real risk of theft, due to both private threat actors e.g. thefts from MtGox, Bitfinex, and scores of others, as well as public threat actors e.g. EO 6102.[2][3]
>>
>> Despite this very real and large-scale theft risk, nobody is proposing that we freeze coins held on exchanges. And yet some people find this (freezing coins) to be a reasonable response to the risk of cryptographic breaks (approximately 6.5 millions coins at risk).[4][5] Curious! But I digress.
>>
>> > This brings us to the question then how at all Bitcoin users can
>> > migrate to new cryptography, because we cannot assume that secp256k1
>> > will last forever. And I think the answer is essentially that it
>> > requires the entire ecosystem to change their assumptions. This does
>> > not mean that adding a new opt-in cryptographic primitive is infeasible
>> > or a bad idea; it just means that adding FancySig as an option is
>> > changing the collective security assumption from "secp256k1 is secure"
>> > to "secp256k1 AND FancySig are secure" once FancySig gets adopted at
>> > scale, and the discussion about adding new primitives should be treated
>> > with the gravity that entails. And it means that disabling secp256k1 EC
>> > operations (or near-everyone migrating to FancySig, but I think that is
>> > unlikely) is the only way to change the collective security assumption
>> > from "secp256k1 AND FancySig are secure" to "FancySig is secure".
>> >
>> > Because of that, if CRQCs or other EC-breaks become reality, or just
>> > the fear about them becomes significant enough, I do believe that
>> > disabling EC opcodes will be necessary in any economically-relevant
>> > surviving chain, due to the millions of BTC that are unlikely to ever
>> > move. Note that I am *not* arguing that "Bitcoin" *will*, *should*, or
>> > even *can* do this, and I'm quite sure that the inherent confiscation
>> > required will make the result uninteresting to me personally. It may be
>> > that such disabling only happens in a fork that doesn't end up being
>> > called Bitcoin, or it may be that this happens only after a CRQC has
>> > been demonstrated to exist. Still, given a severe enough threat I think
>> > it is inevitable, and I think that this means we shouldn't worry too
>> > much about what happens in chains in which EC is not disabled while
>> > simultaneously EC is considered insecure: such chains will be worthless
>> > anyway.
>>
>> I don't believe the predominant "collective security assumption" is that "secp256k1 is secure". Everyone using bitcoin, going all the way back to the genesis block, has known (or should know) that secp256k1 is vulnerable to a CRQC, and therefore secp256k1 is not unconditionally secure. So I would rephrase the assumption to be that "secp256k1 is currently secure, and if it is ever at risk of being broken, there is a large incentive for a viable alternative to be discovered, implemented, and adopted by anyone who is concerned about this risk". Note that this assumption does not, and cannot, preclude the possibility that other users store their coins in insecure ways, even en masse (as shown empirically by the above example of millions of coins held by centralized custodians).
>>
>> An alternative where "secp256k1 OR FancySig is secure" seems strictly preferable to me (assuming we have some reasonable degree of confidence in the security of FancySig at the time of activation) than relying only on "secp256k1 is secure".
>>
>> As an aside, I note that because it has been known since before bitcoin even launched that secp256k1 is vulnerable to a CRQC, we cannot rule out the possibility that the people who leave their coins in CRQC-vulnerable addresses -- even after QR addresses are made available -- aren't doing so intentionally, as a kind of bounty for developing a CRQC. Freezing these coins would violate their intentions. This is just one example of the ethical problems associated with such proposals.
>>
>> A perhaps even more fundamental "collective assumption" of bitcoin users is that "a redeem script that was valid at the time that a UTXO was encumbered will always remain valid". This is fundamental to bitcoin's nature as p2p electronic cash. If users woke up one day no longer able to assume that their redeem scripts would remain valid, then they would not be able to rely on bitcoin to store value over time and the system would quickly collapse. Thus, any proposal to disable features in a way that freezes coins is a proposal to destroy bitcoin.
>>
>> Bitcoin can survive a temporary price dump, if that's what ends up happening with vulnerable coins. Bitcoin cannot survive a violation of the fundamental assumption that redeem scripts for existing UTXOs will always remain valid, and certainly not a violation at the scale that you describe.
>>
>> Regards,
>> Light
>>
>> [1] https://www.coinglass.com/Balance
>> [2] https://bitcointalk.org/index.php?topic=5090869.0
>> [3] https://en.wikipedia.org/wiki/Executive_Order_6102
>> [4] https://github.com/bitcoin/bips/pull/1895
>> [5] https://youtu.be/a_B8BnwagEU&t=150
>>
>> On Fri, Feb 13, 2026, at 11:20 AM, Pieter Wuille wrote:
>> > Hi all,
>> >
>> > A thread <https://groups.google.com/g/bitcoindev/c/7jkVS1K9WLo> was
>> > recently started on this list about cryptographic agility in Bitcoin. I
>> > believe there are important limitations around that idea, and wanted to
>> > offer my own perspective. It's more a philosophical consideration, and
>> > is not intended as an argument against (or for) any particular proposal
>> > today.
>> >
>> > The idea is giving users/wallets the ability to choose the
>> > cryptographic primitives used to protect their own coins, from a set of
>> > available primitives that may change over time. I think this ignores
>> > how important it is what *others do with their coins*. If others' coins
>> > lose value, for example due to fears about them becoming vulnerable to
>> > theft with cryptographic breakthroughs, so do your own due to
>> > fungibility, regardless of how well protected they are.
>> >
>> > As an extreme thought-experiment, imagine that tomorrow a new
>> > cryptographic signature scheme FancySig is published, with all the
>> > features that Bitcoin relies on today: small signatures, fast to
>> > verify, presumed post-quantum, BIP32-like derivation, taproot-like
>> > tweaking, multisignatures, thresholds, ... Further assume that within
>> > the next year or two, voices (A) start appearing arguing that such a
>> > scheme should be adopted, because it's the silver bullet the ecosystem
>> > has been waiting for. At the same time, another camp (B) may appear
>> > cautioning against this, because the scheme is new, hasn't stood the
>> > test of time, and isn't well-analyzed. These two camps may find
>> > themselves in a fundamental disagreement:
>> >
>> >  • Camp (A), fearing an EC-break (CRQC or otherwise), wouldn't just
>> > want FancySig as an option - they would want (feasible or not) that
>> > *near-everyone migrates to it*, because the prospect of millions of BTC
>> > in EC-vulnerable coins threatens their own hodling.
>> >  • Camp (B), fearing the possibility that FancySig gets broken soon,
>> > possibly even classically
>> > <https://www.quantamagazine.org/post-quantum-cryptography-scheme-is-cracked-on-a-laptop-20220824/>,
>> > don't want to just not use FancySig; they would want *near-nobody to
>> > migrate to it*, because the prospect of a potential break of FancySig
>> > threatens their own hodling.
>> > This is of course an extreme scenario, and in reality the divergence
>> > between camps may be much less incompatible, but I still think it's a
>> > good demonstration of the fact that *despite being a currency for
>> > enemies, Bitcoin essentially requires users to share trust assumptions
>> > in the cryptography, and its technology in general*.
>> >
>> > A small note aside: you can argue that it is possible for people to
>> > store coins insecurely, like in an OP_TRUE script output, or with
>> > private keys that are made public. I don't think this possibility
>> > affects the point above, because it is not about what possibilities
>> > exist, but which approaches people are likely to / asked to adopt.
>> > Nobody is incentivized or encouraged to store coins in an OP_TRUE.
>> >
>> > It is also good to ask what amounts are relevant here, to which I do
>> > not know the answer. Possibly, the prospect of 100k BTC becoming
>> > vulnerable to theft won't threaten the value of the other coins, while
>> > the prospect of 10M BTC becoming vulnerable may. Depending on where
>> > your belief about this lies, you may end up with very different
>> > conclusions. Still, to me it is clear that *some* threshold exists
>> > above which I would be uncomfortable with seeing that many coins move
>> > into an untrustworthy scheme, even if they are not my own coins.
>> >
>> > This brings us to the question then how at all Bitcoin users can
>> > migrate to new cryptography, because we cannot assume that secp256k1
>> > will last forever. And I think the answer is essentially that it
>> > requires the entire ecosystem to change their assumptions. This does
>> > not mean that adding a new opt-in cryptographic primitive is infeasible
>> > or a bad idea; it just means that adding FancySig as an option is
>> > changing the collective security assumption from "secp256k1 is secure"
>> > to "secp256k1 AND FancySig are secure" once FancySig gets adopted at
>> > scale, and the discussion about adding new primitives should be treated
>> > with the gravity that entails. And it means that disabling secp256k1 EC
>> > operations (or near-everyone migrating to FancySig, but I think that is
>> > unlikely) is the only way to change the collective security assumption
>> > from "secp256k1 AND FancySig are secure" to "FancySig is secure".
>> >
>> > Because of that, if CRQCs or other EC-breaks become reality, or just
>> > the fear about them becomes significant enough, I do believe that
>> > disabling EC opcodes will be necessary in any economically-relevant
>> > surviving chain, due to the millions of BTC that are unlikely to ever
>> > move. Note that I am *not* arguing that "Bitcoin" *will*, *should*, or
>> > even *can* do this, and I'm quite sure that the inherent confiscation
>> > required will make the result uninteresting to me personally. It may be
>> > that such disabling only happens in a fork that doesn't end up being
>> > called Bitcoin, or it may be that this happens only after a CRQC has
>> > been demonstrated to exist. Still, given a severe enough threat I think
>> > it is inevitable, and I think that this means we shouldn't worry too
>> > much about what happens in chains in which EC is not disabled while
>> > simultaneously EC is considered insecure: such chains will be worthless
>> > anyway.
>> >
>> > --
>> > Pieter
>> >
>> >
>> >
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