[amelius]

Except there are two people, B and C with noise. The only thing you can prove is that if you XOR both noise vectors together, you have a copyrighted work.

Both people will say they are innocent and that the other person used the other's noise vector and the copyrighted work to produce their noise vector.

[aleph_minus_one]

> Both people will say they are innocent and that the other person used the other's noise vector and the copyrighted work to produce their noise vector.

Simple: because you can't find out who tells the truth, simply jail both. :-)

[TeMPOraL]

More importantly, both are obviously colluding in the infringement, and are fully aware they have copyrighted data.

See also: https://xkcd.com/1494/

[amelius]

You can apply the same to tax fraud. Hey what if I move this subsidiary company to Panama, etc. Still everybody does it and gets away with it.

[amelius]

But the XOR trick scales to many people.

Are you going to jail 100 people because one of them is lying?

[fwip]

If they are all posting their noise vectors up on xor-music.com, sure. If they have valid reasons for making available a specific 'noise' vector (maybe they can prove it decrypts to something useful), then probably not.

Judges and juries don't need to guilt to be mathematically proved, they just have to be pretty sure.

[amelius]

What if xor-music.com also distributes legal content?

[fwip]

Then the jury will weigh the evidence and come to a decision.

[TeMPOraL]

Yes. Or at least hint at it, at which point someone will probably volunteer or let slip some information that gives you a rough shape of the causal chain, at which point you know where to dig and pressure further, and eventually convince someone to confess or get a warrant to be sure.

If the prosecuting side has a reason to care that much, it doesn't matter whether it's 10 or 100 people - in fact, if it's 100 people, the original source is in deeper shit because this is now obviously not just personal use, but distribution.

[amelius]

Sounds nice on paper but it becomes exponentially difficult when many people are involved, and some groups of the vectors XOR'ed together also demonstrably result in legal content.