Subject: Re: [bitcoindev] Re: A Post Quantum Migration Proposal

From: Marin Ivezic <[email-masked]>
Date: Sun, 20 Jul 2025 10:39:47 -0700 (PDT)

Even a year ago it was totally fair to question the feasibility of CRQCs. 
After all the recent scientific and engineering wins, that is not in 
question anymore. Eventual arrival of CRQC is pretty much a consensus now 
in quantum and cyber communities.

But that question is almost irrelevant now. The world is acting like CRQCs 
are coming, so we should act like it too. Regulators and governments are 
issuing quantum readiness roadmaps, banks have started their programs, 
insurers are carving out quantum risks, shareholders and analysts are 
questioning quantum readiness on earnings calls… and the media is eating it 
all up. The general public awareness is rapidly growing.

Rightly or wrongly, users will soon expect to see some assurances or plans 
on how bitcoin will resist the quantum threat. And if our response is that 
a few on the list think CRQC are laughable, the confidence will take a big 
hit.

The proposed BIP makes lots of sense. With that and BIP-360, a plan is 
shaping. And then we need three almost independent discussions:
1. We could technically solve Phase C (Post-Quantum Legacy Recovery) for 
any impacted BIP-39 wallets. This is the (relatively) easy one.
2. How do we make it all a bit more “crypto-agile”?
3. And finally the philosophical discussion on how to treat legacy non-HD 
wallets - burn them or allow them to be “stolen” / “liberated”.
Best, 
Marin
On Sunday, July 20, 2025 at 6:07:01 PM UTC+2 conduition wrote:

> Hi Peter,
>
> I think everyone here is well-aware of the possibility
> that CRQCs may not ever appear, but that doesn't change
> the fact we must have a plan ready to handle them. Lopp's
> proposal does exactly that, and in a way that can be
> rolled out incrementally as the risk increases. And even
> if CRQCs never break discrete log, we would do well to
> invest the time in designing this migration path anyway.
> We'd then have a playbook to handle other sources of
> cryptanalytic breakthroughs in the future.
>
> I think you're worried the community may jump the gun and
> deploy a freezing upgrade like phases A or B too early. I
> share your concern but if anything I suspect the opposite
> will happen. Nobody is going to be willing to freeze
> anything unless imminent danger is readily apparent, and
> fear-based reactions kick in.
>
> Once it does, things will happen fast, and we need a plan
> ready for that day (if it comes).
>
> regards,
> conduition
>
>
>
> On Saturday, July 19th, 2025 at 8:13 AM, Peter Todd <[email-masked]> 
> wrote:
>
> > On Mon, Jul 14, 2025 at 02:52:17PM -0400, Jameson Lopp wrote:
> >
> > > Correct, this time is different in that we're not talking about vague
> > > unknown weaknesses. Rather, we're talking about a known algorithm that
> > > makes breaking cryptographic primitives orders of magnitude cheaper.
> >
> >
> > We already have known algorithms that would break cryptographic 
> primitives if
> > sufficiently good analog computers actually existed. Or for that matter, 
> "split
> > the universe" brute forcing. No-one is worried about them because 
> "sufficiently
> > good" analog computers and multiverses are widely belived to not be 
> physically
> > realizable.
> >
> > For all the claims of progress on quantum computing hardware, the fact 
> still
> > remains that no-one is even close to demonstrating cryptographic-relevant
> > quantum computing capabilities and the actual cryptographic-relevant
> > capabilities of real hardware are laughable. It's still an unknown 
> whether or
> > not they are physically possible, and outside of the part of the physics
> > community that would like to sell you a quantum computer - or research
> > developing one - they're widely belived to be not physical.
> >
> > Hence, these are still vague unknown weaknesses. Until progress is less 
> vague,
> > actively freezing peoples' coins is not going to happen.
> >
> > --
> > https://petertodd.org 'peter'[:-1]@petertodd.org
> >
> > --
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> .

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