He imported this single key into a modern, fresh wallet on his online machine. He didn't need to sync the whole blockchain history. He just needed to see if the network recognized the key.
To the paranoid, it is a nightmare. To the opportunistic, it is a lottery ticket. To the security professional, it is a reminder that the blockchain is immutable—but the humans using it are gloriously, dangerously fallible. indexofbitcoinwalletdat upd
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