I have made an open source airgapped device for signing bundles offline.
A main purpose is to address the possiblity that the components we use to make our devices are already compromised before they are purchased and yet we still need to use these devices to work with seeds.
So let's imagine I sign a bundle on an infected machine which may have changed the amount of the transactions and also the recipient's address to that of an attacker.
To check for this I would like to broadcast the bundle to the TestNet first to see how much the transactions are and where they are sent.
I understand that sending multiple transactions from the same address gives away information that makes it easier to brute force the seed.
I have two questions:
1. Is the idea basically sound?
2. Does broadcasting a bundle on both MainNet and TestNet facilitate brute forcing the seed?
Thanks for your help.