So what happens if I violate the block chain ?

[JeromeS]

I still don't get it... doesn't what you say contradict the bolded part above?

If everyone prunes a certain transaction (the content) from the block, the block is still valid and nothing has to be re-mined. However, checking validity of another transactios input that uses an output of the pruned transaction cannot be done any more?

Could someone please explain?

Sorry, I wasn't thinking about the double spending limitation. I meant that you can verify that a transaction belongs in a merkle tree and a merkle tree belongs to a block, but you still need to trust that another (full) node verified that that block doesn't spend any inputs that have already been spent.

Not to derail this thread, but I too would like an explanation as to how lightweight and pruned clients handle this. I'm guessing they rely on the fact that only the bitcoin network has enough power to produce new block hashes that match the target difficulty ?

[davout]

Not to derail this thread, but I too would like an explanation as to how lightweight and pruned clients handle this. I'm guessing they rely on the fact that only the bitcoin network has enough power to produce new block hashes that match the target difficulty ?

Lightweight clients aren't zero-trust, pruned clients are. You should read the wiki.

[FreeMoney]

Requirements would be:
1. someone to inject this data in to block chain
2. someone creating and distributing a program that can read this data as an image file
3. somone telling you where in the blockchain to find the offending data (a "link")
4. no one to take action to remove the data from the blockchain again

Now, since it's of no use/harm to have data that has the potential to be read by some program, if it never actually is read as such.

This means, that for this to be a real problem, you have to have someone publically sharing the "link" to this information. As long as you can cut the "link" sharing, then the offending data is not a problem on it's own.

A program can be made that will display bad pictures when fed this post as data.

You still need:
1. someone to inject this data in to block chain
2. someone creating and distributing a program that can read this data as an image file
3. somone telling you where in the blockchain to find the offending data (a "link")
4. no one to take action to remove the data from the blockchain again

You don't need to inject anything. You can write a program that when fed the genesis block it makes an illegal pattern of pixels come up on the screen. So only 2 and 3 need to happen.