mandatory-script-verify-flag-failed (Withdraw proof validation failed - output does not match expected about elements

[apoelstra]

Hi @Christewart, sorry for the delay in investigating this. This is a bug in sidechain-manipulation.py.

It's an alpha consensus rule that any sidechain claim transactions have a locked sidechain output as input, then your address as output, follow immediately by a change output whose scriptPubKey is identical to the scriptPubKey of the original locked output. That is, you are "putting the change back where it came from".

In sidechain-manipulation.py:231 the change output is hardcoded to be the same as the alpha genesis output (which describes 21m coins with no corresponding locked Testnet output). However, the genesis output is not the only locked sidechain output; there are other outputs which correspond to coins users have locked when withdrawing from Alpha to Testnet.

So the bug you're seeing is that sidechain-manipulation.py is trying to unlock some locked output created by some user (so it does not originate from the genesis output), then send the coins (a) to you, and (b) "back" to the genesis output.

So the script needs to be fixed to look at which output it's spending, and to use that.

cc @TheBlueMatt can I just have UTXOFinder store its scriptpubkey then assign that to relock_scriptPubKey on line 231?

[TomMcCabe]

@Sarodh The secondScriptPubKeyHash is just the hash of the secondScriptPubKey.

secondScriptPubKey: OP_DROP 144 OP_LESSTHANOREQUAL (from sidechain-manipulation.py)

In hex: 75029000a1

Sha256(Ripemd160(secondScriptPubKey)) == 9eac001049d5c38ece8996485418421f4a01e2d7

[Sarodh]

Thanks @TomMcCabe

[instagibbs]

peg-in system was overhauled