Xpress Validation - request for input

[Chronos]

I guess I'm trying to ask: would the block be rejected by a node running Xpress Validation? Sorry if I keep repeating myself, but it's not clear to me that such a node would catch that scenario or not, since the transactions were already pre-validated before the block was received.

You can always say that a miner won't mine a bad block, but by that logic, no validation is ever required. The entire point of validation is to assume that a miner might mine something unexpected.

 

[Peter Tschipper]

No worries about questions...

Bypassing the later re-validation of a tx doesn't mean the block will automatically get accepted, there are other block checks that have to pass, everything has to line up. All we're saying is that the tx we've added to the block is a valid one, and it exists in the block (xthin) that was sent to us, but whether the block finally is valid is for other checks to determine, and there are numerous other checks.

So in your case, an invalid xthin block was sent to us with all valid tx hashes in it. We re-construct the block, skipping the tx validation because they are valid tx's, and it finally will be rejected as any other invalid block would be. Where exactly that failure in this case would be I don't know but I would suspect one that the UTXO would not update, the merkleroot or proof of work would not be valid or something possibly else?