In January’2016 a Russian national who bought 10,000 USD worth of Bitcoin well before the boom period had unfortunately forgotten the password after encrypting the private keys in a zip file!

Surprisingly as luck would have it the Russian (The Guy) managed to find Michael Stay, a former Google security engineer who had published a paper on methods to decrypt encoded zip files some twenty years ago.

Some months back ‘The Guy’ sent a message to Stay explaining about himself losing access to Bitcoin private keys and wanted his help in recovering the now $300,000 worth of bitcoins back.

In his talk this week at the DEFCON Security Conference Michael Stay detailed the attempts to break in and retrieve the BTC.

After analyzing the problem initially Stay estimated $100,000 as charges as it was impossible to get into the zip file with the available tools as it used the ZIP 2.0 Legacy encryption.’The Guy’ agreed to pay as after all he would still be in profit with the remaining balance.

Stay started narrowing down on the possibilities of gaining access to the password key-file in ‘quintillions’ even after ‘The Guy’ knowing the zip program version and file creation time stamp!

Stay started working together with Pyrofex CEO Nash Forster by implementing the crypt-analysis code and running it on Nvidia Tesla general purpose GPU’s.

After a lengthy breakthrough and failure in between the duo Stay and Forster started working on Stay’s alternative method which finally provided the breakthrough and they were able to get in and retrieve the Bitcoin private keys.

The total costs worked out to $6,000 to $7,000 USD far much lesser than the previously quoted $100,000 USD.

‘The Guy’ finally paid $25,000 for the successful assignment.

Readers can watch the full video where Michael Stay explains how he managed to recover Bitcoin from the encrypted file :-

Thanks for Reading!