I want to prove the total sum of BTC I have access to. Therefore I think if I use message signing to assert "owned by makerofthings7" in each address, then anyone can compute the total coins in my wallet based on that assertion.
If we only focus on the encryption part (and not what the QT client permits), what is the most efficient way to prove that I control the funds of many addresses?
Are all addresses in my wallet that contain coins available for signing & verification? In particular what happens to the "change" addresses that are dynamically created when sending and receiving Tx?
Can I have a single signed message that is signed by all the keys in my wallet?