Subject: Re: [bitcoindev] Reiterating centralized coinjoin (Wasabi & Samourai) deanonymization attacks

From: Peter Todd <[email-masked]>
Date: Fri, 24 Jan 2025 16:00:28 +0000

On Thu, Jan 23, 2025 at 04:25:46PM +0000, Peter Todd wrote:
> The only question left for this technique is a cryptography one:
> 
> Is it possible to create an alternate pubkey p', that such that a valid
> signature s signed by arbitrary pubkey p for message m, also validates
> for p' for signature s and message m? I believe the answer is no for
> schnorr. But I'm not a cryptography expert, and I may have missed
> something.

Sorry, I forgot one condition in that paragraph. Here's what it should
have said:

Is it possible to create an alternate pubkey p', that such that a valid
signature s signed by arbitrary pubkey p for message m, also validates
for p' for signature s and message m, *and* also validates for signature
s' and message m'? I believe the answer is no for schnorr. But I'm not a
cryptography expert, and I may have missed something.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

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