From: Ethan Heilman <eth3rs@gmail.com>
To: Erik Aronesty <erik@q32.com>
Cc: conduition <conduition@proton.me>,
"garlonicon@gmail.com" <garlonicon@gmail.com>,
Jonas Nick <jonasd.nick@gmail.com>,
bitcoindev@googlegroups.com
Subject: Re: [bitcoindev] Algorithm Agility for Bitcoin to maintain security in the face of quantum and classic breaks in the signature algorithms
Date: Mon, 23 Feb 2026 16:42:50 -0500 [thread overview]
Message-ID: <CAEM=y+WAR3YXmdrrT-zN210ob53dmYC1KZwBZ=OK2bKgNeAHUg@mail.gmail.com> (raw)
In-Reply-To: <CAJowKgL+YMWSgEPcVF-u8bNvPFK35cY-3cHtimWD2mtXdDhUzQ@mail.gmail.com>
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> I thought "tweaking", in general, is lost in SPHINCS, as well as
multiparty sigs. Be interested to see those solutions. But, regardless,
17kb sigs are... not compatible with a decentralized bitcoin, imo.
Lattice-sigs are the only reasonable PQ way forward and they aren't ready
yet.
SPHINCS is ~8kb (7,888 bytes) not 17kb.
SPHINCS SLH-DSA-128s has 32 byte public keys and 7,856 byte signatures
Total size of 7,888 bytes not 17kb.
The Lattice sigs aren't that much better than SPHINCS
CRYSTALS-Dilithium ML-DSA has 1,312 byte public keys and 2,420 byte
signatures
Total size of 3,732 bytes.
Falcon has 897 byte public keys and 666 signatures
1,563 bytes
ML-DSA currently has the most support in the Lattice world, but it is still
too large to be a drop in replacement for ECC without a witness discount.
If we had to choose tomorrow, I'd advocate for ML-DSA with a massive
witness discount, but I'd be very unhappy with the witness discount. If the
witness discount was out of the question, then I'd advocate for something
similar to 324-byte stateful hash based SHRINCS signature. Neither is ideal.
My current thinking is to use SLH-DSA as a backup. This keeps us safe if
everything goes wrong and allows us to reach safety early so we can take
time to determine the right drop-in replacement for ECC. Hopefully in 3
years, SQI-sign is fast enough to be considered.
On Mon, Feb 23, 2026 at 2:08 PM Erik Aronesty <erik@q32.com> wrote:
>
>>
>> I'd be excited to learn about this as an option. Erik, could you please
>> answer my previous questions about the viability of your linked protocol?
>> I'm not questioning its quantum-resistance properties (yet). I'm wondering
>> how it is possible to instantiate this scheme in a way that allows a wallet
>> to actually use this commit/reveal scheme without knowing the final
>> destination CTV templates (denoted T & E in the delving post) in advance of
>> creating the phase 0 locking script.
>>
>
> I provided an example script that shows how it works:
> https://gist.github.com/earonesty/ea086aa995be1a860af093f93bd45bf2. you
> don't pin to the final destination in phase 0.
>
> txhash is a partial-commitment, not over all fields. this give the
> flexibility needed for the final spend, since you don't commit to it.
>
> however someone has pointed out a fee-problem that CCV's value-aware
> composability can solve. coming around to thinking the ccv-based
> construction would be necessary. CCV is more powerful but requires much
> more care in policy and analysis. CTV is trivial, we could merge it
> tomorrow and hardly worry about surface area issues. TXHASH is only
> slightly more complicated. CCV has a much bigger burden of proof around
> implementation and node safety... but i think you could do many kinds of
> vaulting schemes with it alone.
>
>
> But in the case of hash-based signature (HBS) schemes, i disagree. HBS is
>> already mature. Whatever cryptanalytic breakthroughs the future holds, we
>> can be reasonably sure that SHA256 preimage resistance will hold for a long
>> time, so HBS security will hold. Even today md4 and md5 preimage resistance
>> still holds. Securing coins using hashes alone is the ideal fallback, and
>> even if HBS is not the most efficient class of schemes, that doesn't matter
>> so much if we don't use HBS as our primary everyday signature scheme. Its
>> value lies in security, not efficiency.
>>
>
> When I mean "too soon", I'm including SPHINCS, not sure what
>
> 1. Earlier versions of the SPHINCS framework were found to be susceptible
> to fault attacks
> 2. Earlier "Tight" proof for v1 SPHINCS was flawed, leading to 60 bits of
> security, not 128
>
> > If you're worried about stuff like how xpubs would work with HBS, we
> have solutions for that too, and they are mostly drop-in replacements for
> existing standards.
>
> I thought "tweaking", in general, is lost in SPHINCS, as well as
> multiparty sigs. Be interested to see those solutions. But, regardless,
> 17kb sigs are... not compatible with a decentralized bitcoin, imo.
> Lattice-sigs are the only reasonable PQ way forward and they aren't ready
> yet.
>
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next prev parent reply other threads:[~2026-02-23 22:03 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 14:20 Ethan Heilman
2026-02-10 8:53 ` Jonas Nick
2026-02-10 16:44 ` Ethan Heilman
[not found] ` <CAJowKg+WJLAJoMhyhVfkC9OSdks5jBieDWty9ce-Qju-84URFA@mail.gmail.com>
2026-02-10 23:13 ` Ethan Heilman
2026-02-11 0:19 ` Erik Aronesty
2026-02-11 2:40 ` Ethan Heilman
2026-02-11 7:25 ` Erik Aronesty
2026-02-11 16:37 ` Ethan Heilman
2026-02-17 4:13 ` 'conduition' via Bitcoin Development Mailing List
2026-02-17 7:39 ` 'conduition' via Bitcoin Development Mailing List
2026-02-19 14:35 ` Garlo Nicon
2026-02-20 1:41 ` Alex
2026-02-20 18:48 ` Erik Aronesty
2026-02-23 14:00 ` 'conduition' via Bitcoin Development Mailing List
2026-02-23 19:08 ` Erik Aronesty
2026-02-23 21:42 ` Ethan Heilman [this message]
2026-02-24 0:12 ` Alex
2026-02-25 10:43 ` Javier Mateos
2026-02-26 13:24 ` 'Mikhail Kudinov' via Bitcoin Development Mailing List
2026-02-26 15:51 ` Matt Corallo
2026-02-27 15:18 ` 'Mikhail Kudinov' via Bitcoin Development Mailing List
2026-02-27 19:31 ` 'conduition' via Bitcoin Development Mailing List
2026-03-01 12:24 ` 'Mikhail Kudinov' via Bitcoin Development Mailing List
2026-03-01 21:28 ` Alex
2026-02-11 18:53 ` Matt Corallo
2026-02-11 22:57 ` Ethan Heilman
2026-02-12 14:55 ` Matt Corallo
2026-02-12 15:35 ` Alex
2026-02-12 19:20 ` Matt Corallo
2026-02-12 18:08 ` Ethan Heilman
2026-02-12 19:13 ` Matt Corallo
2026-02-12 20:35 ` Ethan Heilman
2026-02-12 20:43 ` Matt Corallo
2026-02-12 15:13 ` Alex
2026-02-12 19:16 ` Matt Corallo
2026-02-12 15:36 ` waxwing/ AdamISZ
2026-02-12 19:35 ` Matt Corallo
2026-02-12 19:43 ` Matt Corallo
2026-02-14 12:39 ` waxwing/ AdamISZ
2026-02-15 12:12 ` Matt Corallo
2026-02-10 21:51 ` 'Brandon Black' via Bitcoin Development Mailing List
2026-02-10 22:19 ` Ethan Heilman
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