Subject: Re: [bitcoindev] Relax OP_RETURN standardness restrictions

From: Luke Dashjr <[email-masked]>
Date: Sat, 26 Apr 2025 05:50:54 -0400

It should be needless to say, but this idea is utter insanity. 
Disappointing to see positive responses, and not one sensible reply 
calling it out yet. The bugs should be fixed, not the abuse embraced. If 
attackers continue to bypass filters, we can go back to a full whitelist 
approach. We're now 2+ years into this wave of attacks, and the damage 
it has already done should be more than enough to prove the hands-off 
attitude is not viable. Am I the only one left on this list who actually 
cares about Bitcoin's survival?

On 4/17/25 14:52, 'Antoine Poinsot' via Bitcoin Development Mailing List 
wrote:
> Hi,
>
> Standardness rules exist for 3 mains reasons: mitigate DoS vectors, 
> provide upgrade hooks, or as a nudge to deter some usages.
>
> Bitcoin Core will by default only relay and mine transactions with at 
> most a single OP_RETURN output, with a scriptPubKey no larger than 83 
> bytes. This standardness rule falls into the third category: it aims 
> to mildly deter data storage while still allowing a less harmful 
> alternative than using non-provably-unspendable outputs.
>
> Developers are now designing constructions that work around these 
> limitations. An example is Clementine, the recently-announced Citrea 
> bridge, which uses unspendable Taproot outputs to store data in its 
> "WatchtowerChallenge" transaction due to the standardness restrictions 
> on the size of OP_RETURNs[^0]. Meanwhile, we have witnessed in recent 
> years that the nudge is ineffective to deter storing data onchain.
>
> Since the restrictions on the usage of OP_RETURN outputs encourage 
> harmful practices while being ineffective in deterring unwanted usage, 
> i propose to drop them. I suggest to start by lifting the restriction 
> on the size of the scriptPubKey for OP_RETURN outputs, as a first 
> minimal step to stop encouraging harmful behaviour, and to then 
> proceed to lift the restriction on the number of OP_RETURN outputs per 
> transactions.
>
> Antoine Poinsot
>
> [^0]: See section 6.1 of their whitepaper here 
> https://citrea.xyz/clementine_whitepaper.pdf
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