And perhaps worse, what happens if someone steals/copies your private key (say your paper backup) and signs a change of address in your name? Can you convince a

And perhaps worse, what happens if someone steals/copies your private key (say your paper backup) and signs a change of address in your name? Can you convince authorities that you didn't actually make the change? Maybe if it is a physical address. After all, you presumably live there. But what if it's just some payment contract? As far as they care you yourself signed it, and they have the proof. If you can get them to cancel the contract, what was the point of using blockchain anyway?