Ownership of the account is determined by possession of the private key. Only the one with the key can spend from the account.
In Bitcoin the way to implement this would be by transferring any funds in the account first to a time-locked escrow account and then to a new account for which the challenger possesses the key. It's doable but probably not worthwhile; IMHO the effort would be better spent on ensuring that you don't lose the key in the first place.
In Bitcoin the way to implement this would be by transferring any funds in the account first to a time-locked escrow account and then to a new account for which the challenger possesses the key. It's doable but probably not worthwhile; IMHO the effort would be better spent on ensuring that you don't lose the key in the first place.