Subject: Re: [bitcoindev] Against Allowing Quantum Recovery of Bitcoin

From: Javier Mateos <[email-masked]>
Date: Sun, 30 Mar 2025 15:23:17 -0700 (PDT)

Hi everyone!

Seeing the discussions about transitioning to quantum-resistant signatures, 
I notice three main concerns:

   - 
   
   What should be done with vulnerable funds? Freeze them or leave them 
   exposed?
   - 
   
   How can the transition be made without affecting Bitcoin’s stability or 
   dividing the community?
   - 
   
   How can we avoid market chaos if the transition is disorderly?
   
Personally, I believe the key is a gradual, well-planned transition based 
on incentives rather than abrupt changes that create uncertainty.

I can think of a three-phase approach:

🔹 First, allow users to add optional PQC keys to their Taproot addresses 
starting now.
🔹 Then, before the quantum threat becomes real, introduce a soft fork that 
disables vulnerable signatures, but with a long migration period (at least 
four years).
🔹 Finally, when the threat is imminent, gradually phase out old signatures 
instead of forcing a sudden change.

For this to work, adoption should be incentivized—for example, with lower 
fees for secure transactions and wallet tools that facilitate a smooth 
transition. Additionally, real-time monitoring of vulnerable addresses 
would help mitigate risks.

Another key point is to avoid panic. Instead of a sudden "D-Day" where 
everything changes at once, the deactivation of old UTXOs should be 
gradual, with clear communication so no one feels forced or disadvantaged.

In summary, this is not about imposing rules or confiscating anything, but 
about providing options for an orderly transition that doesn’t compromise 
Bitcoin’s philosophy.

-Javier Mateos

El viernes, 28 de marzo de 2025 a las 21:02:43 UTC-3, Matt Corallo escribió:

>
>
> On 3/25/25 4:16 AM, Sjors Provoost wrote:
> > Matt Corallo wrote:
> > 
> >>> In that scenario you'd need to use a NUMS point for the key path. Or 
> maybe that's unsafe, in which case we'd need a new Taproot version without 
> key path support (or BIP360). That's also not a difficult soft fork, but 
> now again you have something that only a small set of users will want to 
> use.
> >>>>
> >>>>
> >> A NUMS point does not suffice unless we explicitly soft-fork out 
> spending from that NUMS point (which is, of course, doable).
> > 
> > This could be a solution to the sequencing conundrum that I tried to 
> explain.
> > 
> > Along with the first PCQ scheme for tapscript (script path), we could 
> have a soft that disables one or more NUMS points. The latter has zero 
> effect under the current cryptographic assumptions, so it's not 
> confiscatory.
> > 
> > That way people can start using the scheme without having to worry about 
> whether the community decides to freeze key path spending in time. They'll 
> still worry about the market value of their coins, but not about whether 
> they're going to be the first victim (or the umpteenth victim while 
> everyone is in denial and blames them for poor key management).
>
>
> Mmm, yea, fair enough, that seems perfectly reasonable to include.
>
> Matt
>

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