> An interesting possibility is that illegal content gets permanently inserted into a blockchain, which could make running, for example, an ethereum node very illegal.

I've heard this called a "pee in the pool attack."

Block chains like Ethereum and Bitcoin have one intrinsic defense: they don't support very large data objects. So that makes inserting CP problematic. But someone determined enough and willing to spend money could insert a really horrible image as a series of transactions.

At that point you'd need additional data (which transactions) and software in order to stitch things back together, at which point is it the (disjointed, seemingly random) data that's illegal, or the instruction set that allows you to assemble it into something illegal?

If it was the disjointed seemingly random data that was illegal I think that would make the number π illegal too.

Mens rea vs. factus rea.

How about cases where there's not much data involved but it's still questionable whether or not the data is legal to share?

Leaked encryption keys for example come to mind, but I'm sure there's other examples.

That one Blu-ray code would be interesting to see play out in a web3 world.

E: I realise after digging it back up it's what you said with encryption keys but maybe someone else wants to look at the link too or whatever

https://en.wikipedia.org/wiki/AACS_encryption_key_controvers...

Has there been a case of an encryption key successfully being censored?

They tried to censor the blu-ray key, but that survived 3 years before bitcoin was invented

has there been a documented case of this happening yet? one would think that there must have been, at some point, by now. but then I suppose if someone were to make a program that accesses intentionally-inserted distributed immutable data in a blockchain and reconstructs an illegal file (probably an image), then I suppose that executable or source repository itself would then be taken down by authorities and its author(s) prosecuted. but to my knowledge, this hasn't actually happened yet...

You don’t need a program to do that, you can easily embed a BMP or an SVG without a complex executable needed to decode the image heck even for more complex file format a BASE64 decoder can do that.

Also if say CP is currently distributed through compressed archives even if they are PW protected it’s not like that 7zip then somehow becomes the illicit material. If you host the archive you are on the hook of distributing CP even if it’s encrypted…

At least for Bitcoin, there's another defense: what the blockchain actually stores on each block is the root of a Merkle tree which has the transactions as leaves. It's possible to discard unwanted transactions, and that only loses the ability of verifying newer transactions which chain to these discarded transactions. (AFAIK, the original intention was that most nodes would discard old "spent" transactions, to reduce the size of their local database.)

How do you verify new transactions without checking every single past transaction? As far as I understand, you need to know the current balance of every wallet in order to prevent double-spending.

Or adding someone's personally identifying information.. birthdates, addresses, SSN, etc.

Or by running your botnet's C2 on it. There's no kill switch or sinkholing your botnet without killing the entire blockchain.

You could cut off access to the blockchain instead

This has already happened. Nobody seems to care.

https://www.theguardian.com/technology/2018/mar/20/child-abu...

> Crypto proponents are in favor of there being no technical restrictions that prevent such content being posted

This is precisely why they'll fail (aside from technological issues): the rank and file person on the internet does NOT want a Wild West when they go to visit a news feed. Hell, the average person doesn't even really like curated content. They want a chronological list of things they decide to be relevant and nothing else. Just look at all the complaining every time Instatwitter changes an algorithm and hides the method for sorting by most recent.

And what they don't know yet is that all these big companies, if they use this technology, they're going to use them in very focused ways to reward people and prevent them from abandoning their platforms. Because "free" has many meanings, but none of them are inherently exclusionary from corporate competition.