With the forthcoming lifting in Core v30 of the OP_RETURN data limit to 100KB one of the primary concerns of opponents of the change has been the danger of illegal content appearing within the OP_RETURN’s as contiguous data up to 100KB. This has been dismissed as fear-mongering by the Bitcoin Core community and there has been a lot of name-calling and heightened emotion going back and forth between the two camps. A particular concern cited by opponents has been the precedent of Bitcoin SV suffering from illegal content on its blockchain immediately after making this same change to OP_RETURN.
I would like to see the Bitcoin Core side of the argument, presumably they don’t want illegal content any more than Knots people do – but what assurance can they give us in technical terms why we are safe from it?
I have seen some Bitcoin Core supporters say it does not matter if such material appears on the blockchain because special tools would be needed on the Bitcoin nodes to view such illegal material, and that it is “just inert hex”, eg. this post :
https://x.com/dopemind10/status/1967691600475373989
I am not greatly reassured by this argument. I am currently planning to set up my own Bitcoin node and I would not be comfortable with such illegal material being present on any computer within my home even in obfuscated form. I have no guarantees how law enforcement would interpret such content and I don’t especially want to test them.
I have heard the argument that illegal material can already be put into the blockchain and we can’t stop it, via Taproot or fake pubkeys for example, but the OP_RETURN method is much less obfuscated than those methods, being a contiguous 100KB block of data. It is a significant step closer to hosting illegal material, and in this day and age I can’t imagine anyone who would want to take such a step. Even the slightest hint of association with certain types of illegal material, even with a completely false accusation, can suffice to ruin someone’s reputation and even place them in danger.
One thing that does give some reassurance is that major miners will never mine a block containing illegal material in an OP_RETURN. But what will the scenario be when a small unknown anonymous miner who could be located anywhere in the world is able to mine a block and includes within it illegal material in an OP_RETURN? This could happen every few months or so, a ‘mining lottery’ win. I have surmised that major miners will always be checking the block they are building on, and if it contains bad material then they will instead mine on top of the block below it. So by this logic if most of the major miners adopted that policy the probability that the bad block could get into the chain with the highest accumulative chainwork would be infinitesimally small. But are we guaranteed the majority of major miners will adopt such a policy? Once a few blocks are built on top of a bad block it could be very difficult to construct an alternative chain with greater chainwork.
Outwith the actual blockchain itself the other concern is with illegal material appearing within the mempool on individual nodes. Those not using -datacarriersize option to reduce the OP_RETURN data cap on their node to a low level, and not using Knots, will potentially have illegal content in their RAM. Again I wouldn’t want to be the one explaining to law enforcement how that material got there. And who knows what checks a modern computer operating system might be making and what it may report as telemetry data, and how AI components within that OS may interpret dubious material it detects within the RAM. Again it is running risks that you really don’t want in this day and age where absolutely everything we do electronically is analyzed and tracked by increasingly sophisticated systems and that law enforcement are increasingly using, for example for ‘pre-crime’. What safeguards do we have that under Core v30 nodes will not be exposed to this risk in their RAM?
To me a conservative policy on illegal material within Bitcoin makes most sense, I don’t think a ‘que sera’ approach is going to work well for Bitcoin. However for those who disagree with that statement please give your reasons why a more ‘liberal’ or ‘laissez-faire’ approach may be adequate and provide some supporting evidence or case studies if you can. This is a time of great change in society and I think people across the spectrum need to adapt to the new environment and we need to have a concrete discussion on all the matters that are of concern. As the potentially catastrophic inflation bug CVE-2018-17144 of 2018, caused by a technical oversight within the Bitcoin Core team, shows we need to be very cautious about all changes to Bitcoin. A sudden 1250x increase in OP_RETURN capacity has raised alarm bells throughout the community causing a 10x increase in Knots adoption this year alone despite having much less developer support than Core. What is best for Bitcoin is all that should matter, it doesn’t matter who is right or who is wrong, ego doesn’t play a part in good design or good engineering.
