Armory does not verify on chain tx. It does not process scripts unless it's for its own signing purposes. No amount of new op codes would make a difference. The only thing that matters is block serialization on disk and the P2P layer.
So Armory should just work with BitcoinABC as node?
I just read on their reddit:
"We are currently considering accepting only such protected transactions (currently it is still possible, by opting for it, to get non-SIGHASH-FORKID transactions relayed and mined).
Interested parties are encouraged to read REQ-6-1 , REQ-6-2 and REQ-6-3 of the UAHF specification."
Transactions without the SIGHASH-FORKID would be broadcasted also on the Bitcoin chain and would be terrible/impossible/hard to handle.
My plan was to move the BitcoinABC coins after the split but not my Bitcoins.
Another security aspect is that the signed TX would probably be valid for both chains?
That would mean I would need to move my Bitcoins as well when moving on the BitcoinABC chain?
Armory will work the ABC/BCC/whatever node as long as it respects on disk block format and uses the same P2P layer (although that can vary to an extent, Armory uses maybe 30% of the P2P layer messages).
That's for node compatibility. Replay protection is another thing.
The issue with this kind of rushed forks is that their standard has not even congealed in their heads, let alone on paper/code. I'd suggest you ignore their replay protection proposals and just taint the regular way, i.e. get a tx on one chain, double spend the utxo on the other.
The way to do this is to send a utxo back yourself over and over again until you hit the condition to double spend on the other chain. You have 2 ways around this:
1) If the 2 chains have a consistently different block heights:
Achow's LockTime method is the simplest. You would do it like this:
With 0.96.1, Armory conforms to Core's LockTime guidelines, where it set the LockTime of a Tx to the current top block height. This means the tx can't be mined until the chain hits this height (this is originally to prevent aggressive fee stealing orphan attacks between miners). Post split, you want to use this method on the longest fork first. The locktime guarantees the shorter fork can't mine the tx for a while. Once the tx gets on chain A, you can double spend that utxo on chain B, then taint your coins with the resulting output accordingly.
To do this, you need both nodes for both sides of the fork, pick an output with coin selection, spend it on the longest chain, swap back to the other node, create another tx with the utxo and spend it. You don't need to bother with the locktime field, as Armory sets it to the top block on the chain it is being run against. The only thing you really need to pay attention to is making sure you don't mix and match DB's and chain folders or you'll probably nuke your DB, and you're in for a rebuild & rescan.
Once you have the 2 tx (one on each chain) with a different txid, you're good to go. Use the output newly created with the coin selection GUI to taint your other coins as you see fit.
Note: the locktime feature was introduced in 0.96, but a bug in the in legacy txsigcollect message (the blob of text spit out to pass in between online and offline instances) makes it that the locktime is always forced back to 0 by the signer. Therefor, you need 0.96.1 to do this properly (0.96.0.4-testing has the fix). You need to update both signer and online machine for this work.
2) If the 2 chains have a narrow chain length gap but different transaction throughput:
Use my RBF trick: Create a RBF tx that has a fee low enough that it won't get mined anytime soon on the chain with the low throughput, but will get mined quickly on the chain with high throughput. Once it gets mined there, use the RBF GUI to double spend the utxo in another tx, this time with a large fee so that it gets into the low throughput chain quickly (again the goal is to get 2 tx with different txids on each chain).
You need an online 0.96 to RBF, the offline signer can be as old as 0.92.x. If you are using the script types, you'll need to upgrade your signer however.
In both cases, you are just sending coins back to yourself until you get your condition to double spend on the other chain. This is low risk (you're paying fees over and over at worst) and even with very similar chance, you have a good chance of pulling either method off if you persevere.
