Pruning OP_RETURNs with illegal content

[tzpardi]

All due respect Peter, but being concerned about having illegal data in a system is not absurd

I'm not Peter, but yes it absolutely is absurd.  What is legal is constantly changing and has thousands of different definitions depending on where you happen to be.

The whole point of Bitcoin is technology that works across all borders and allows for consensus everywhere, irrespective of borders and man-made laws.  If you don't like some of the data that gets stored on your computer, you are free to delete it.  But yes, full nodes must keep all data passed to them.  That's how the system works.  It's *good* it works that way.

Yes tools that enable free speech also allow bad guys to say bad things, but having free speech guaranteed by technology is worth that price.  Tor is valuable even if it allows pedos to set up hidden services.  PGP is valuable even if it means the terrorists can plan things.  Bitcoin is valuable even if it means nodes get passed data they don't approve of.  The benefits of these technologies far outweight these concerns, and their preservation is of the utmost importance, far outweighing the concern for the bad things bad people do with them.  Robbers and kidnappers use cars and phones to do the bad things they do -- but would you think it's appropriate that the government should monitor where you go and who you call to make sure that you don't engage in that activity?

There is no tool that only does good things for good people.  There are only tools.  We accept that some tools make life easier for bad people, because they also make life so much better for good people.  Having phones and cars... and Tor and PGP and Bitcoin, is better than a world without those things.  And talking about crippling them so that their bad uses are harder does nothing but cripple the entire system, and subverts the entire point of the technology.

There is no phone that can only be used by good people.  And there is no distributed consensus system that can take any kind of data except illegal data.  And to talk about such a thing is silly... but to *want* such a thing is absurd.

Yes, it is absurd.

I have to agree with that about PGP.

[TierNolan]

One way to help with this is to make P2SH mandatory.

This means that the UTXO set could be stored as a set of hashes.  You don't even have to store the hash target.

UTXO pays to H = hash(output script)

You can store hash(salt | hash(output script)).  The salt isn't really required.

When someone tries to spend the output, they have to provide the output script as part of the P2SH process.

Archive nodes would have to store H though.  Attackers could encode their data in H.

This could be helped by requiring that blocks near the tip include H, but blocks more than 144 blocks deep can encode hash(H).

New blocks

UTXO: pay to H1 = hash(output script)

Old blocks

UTXO: pay H2 = hash(hash(output script))

This ensures that all the long term hashes (H2) have a known H1 that they are a hash of.

This makes it harder to encode info in the hashes.  You could still encode it in the last few bits though.

[CIYAM]

I built a simple testbed that encodes data in "sigs" (that use random K values) and although not the cheapest way to store data (the experiment was two bytes per sig and on an average laptop was taking roughly 15 seconds per byte pair to "mine" the sigs) it demonstrates that it is impossible to stop encoding of whatever data you want in the blockchain without even using OP_RETURN stuff.