The Quest to Liberate $300,000 of Bitcoin From an Old Zip File

The Quest to Liberate $300,000 of Bitcoin From an Old Zip File

The question still remained, though, whether all that GPU-crunching would actually work. After months of hammering on the problem, Stay was finally ready to try. The Guy hadn't given the entire zip file to Stay and Foster; he likely didn't trust that they wouldn't steal his cryptocurrency if they did manage to crack the keys. Instead, because of how encryption is implemented in zip files, he was able to just give Stay and Foster the encrypted "headers," or informational notes about the file, without sharing its actual content. By February, four months after that first LinkedIn message, they queued it all up and started the attack.


It ran for 10 days—and failed. Stay later wrote that he was "heartbroken."


"We'd had lots of bugs before, but the tests I ran on my laptop all worked perfectly," he says now. "If it was a bug, it had to be a subtle one, and I worried that it would take us a long time to find." It didn't help that throughout February, bitcoin's price was dropping, and the value of the zip file's contents with it. The Guy was antsy.


Stay combed through his attack, worried about some obscure, incorrect assumption or a hidden bug. He soon struck on a new idea about which number, or "seed," to try as the starting point for the random number generator used in the cryptographic scheme. The Guy combed the test data as well and noticed an error that occurred if the GPU didn't process the correct password on the first attempt. Stay and Foster fixed the bug. With both of these revisions to the attack in place, they were ready to tr ..

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