Offline signing and change addresses

[Sauderite]

Hello all,
I am working on a secure way of storing some bitcoins with electrum though I do spend them from time to time. My question is on change addresses and in particular how one can verify them on the signing machine.

My setup so far is two electrum machines. A watch-only wallet connected to the net (A) and the machine with the full wallet that has never been connected to the net (B). On machine A, I do my electrum mktx, move the file over to B and verify the file using electrum decoderawtransaction. Sign the hex and move the signature back to A for sending to the network. In analyzing possible methods of attack, one thing an attacker could do if A were hacked is modify the electrum on A to send the change from a transaction to an address he controls. Since change addresses are unique per transaction, I can't verify them obviously with a decoderawtransaction. I see one address in the outputs I recognize and one I do not which I assume to be change. With a sendmany, I see several I recognize and one change address unless I have spent all of the inputs.

So, how do folks here verify the change address does in fact belong to the sending wallet? If the solution is not obvious, I wonder how the hardware signing devices are doing this...

[dabura667]

sign.

verify on online pc before sending.

[jonald_fyookball]

you should see the address in your list of change addresses.
if you dont see it, set the gap limit higher.

[dabura667]

you should see the address in your list of change addresses.
if you dont see it, set the gap limit higher.

Dear OP:

This quote has your solution.

Go into console tab > type the following to generate more addresses without a connection.

Code:

>> wallet.storage.put('gap_limit', 50)

Then type this to generate more change addresses.

Code:

>> wallet.gap_limit_for_change = 50

If you computer is slow, 50 addresses might take a while to generate. maybe just 10 or something.

Once you input the above two commands... it might not show up on the GUI... if it's not showing up:

Click File > Open Wallet and select the wallet you currently have open and click "open" (this forces a reloading of addresses from the file that will refresh the UI with your new addresses.

[Sauderite]

Hi, this is definitely the answer. Thank you for that.
Entering those commands doesn't seem to generate new change addresses on a BIP32 wallet (seed v11) I even tried to call wallet.synchronize() though that may need the network. I am trying to figure out what to execute to get electrum to generate new BIP32 change addresses while offline.