Subject: Re: [bitcoindev] Re: [Draft BIP] Quantum-Resistant Transition Framework for Bitcoin

From: "'Bitcoin Foundation' via Bitcoin Development Mailing List" <[email-masked]>
Date: Tue, 12 Aug 2025 15:47:13 -0700 (PDT)

Dear ArmchairCryptologist,

We appreciate your engagement with our quantum resistance proposal. 
Let us address your points with additional technical context:

*NIST Reference Documentation*The referenced blog post includes a link to 
NIST Internal Report 8547 (Initial Public Draft) [0], which offers critical 
guidance regarding the migration to post-quantum cryptographic standards. 
We strongly recommend thorough review of this document by all stakeholders 
evaluating quantum-resistant solutions.

*Pre-Quantum UTXO Sunset Policy*Regarding the migration of pre-quantum 
UTXOs:

   - Our current draft proposes freezing these outputs around 2033
   - This timeline appears in the "Migration Path: Phased Implementation" 
   section (https://quantum-resistant-bitcoin.bitcoin.foundation)
   - We explicitly designed this as an adjustable parameter
   - Based on community feedback, we're prepared to extend this sunset 
   period beyond 2035

The proposed recovery mechanism provides optional pathways for legacy UTXOs 
while maintaining network security. 

We remain open to community input regarding the sunset period for 
pre-quantum UTXOs. The current 2033 (block 1,327,121) proposal aligns 
conservatively with NIST's recommendation to deprecate ECDSA by 2035 [0], 
though we acknowledge reasonable arguments exist for adjusting this 
timeline.

[0]: https://nvlpubs.nist.gov/nistpubs/ir/2024/NIST.IR.8547.ipd.pdf

On Tuesday, August 12, 2025 at 11:04:32 AM UTC+2 ArmchairCryptologist wrote:

>
> An astute observation. To clarify the quantum computing landscape: 
> Google's current quantum processors do not possess 50 logical qubits, and 
> even if they did, this would be insufficient to compromise ECDSA - let 
> alone RSA-2048, which would require approximately 20 million noisy physical 
> qubits for successful cryptanalysis [0].
>
>
> That paper is pretty old. There is a recent paper from a couple of months 
> ago by the same author (Craig Gidney from Google Quantum AI) claiming 
> that you could break RSA-2048 with around a million noisy qubits in about a 
> week. 
>
> Paper: https://arxiv.org/pdf/2505.15917
> Blog post: 
> https://security.googleblog.com/2025/05/tracking-cost-of-quantum-factori.html
>
> I can't say for sure whether this approach can be applied to ECDSA; I have 
> seen claims before that it has less quantum resistance than RSA-2048, but 
> I'm unsure if this is still considered to be the case. And while these 
> papers are of course largely theoretical in nature since nothing close to 
> the required amount of qubits exists at this point, I haven't seen anyone 
> refute these claim at this point. These is still no hard evidence I'm aware 
> of that a quantum computer capable of breaking ECDSA is inevitable, but 
> given the rate of development, there could be some cause of concern.
>
> Getting post-quantum addresses designed, implemented and activated by 2030 
> in accordance with the recommendations in this paper seems prudent to me, 
> if this is at all possible. Deactivating inactive pre-quantum UTXOs with 
> exposed public keys by 2035 should certainly be considered. But I still 
> don't feel like deactivating pre-quantum UTXOs without exposed public keys 
> in general is warranted, at least until a quantum computer capable of 
> breaking public keys in the short time between they are broadcast and 
> included in a block is known to exist - and even then, only if some 
> scheme could be devised that still allows spending them using some 
> additional cryptographic proof of ownership, ZKP or otherwise.
>
> --
> Best,
> ArmchairCryptologist
>

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