Even after seizing more than 50 million euro (roughly $60 million) worth of Bitcoin from a fraudster, prosecutors in Germany were unable to unlock the money as the man did not give them the password, reported Reuters.

The fraudster was sentenced to jail and has served his term since then, while police tried everything to crack the code to access over 1,700 Bitcoin.

“We asked him but he didn’t say,” prosecutor Sebastian Murer told Reuters on Friday.

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“Perhaps he doesn’t know,” he added.

The fraudster had been jailed for more than two years for covertly installing software on other computers to harness their power to “mine” or produce Bitcoin.

Bitcoin,  a cryptocurrency invented in 2008, is stored on software called ‘digital wallet’, which is secured through encryption. A password is needed to open the wallet and access Bitcoin. When a password is lost the user cannot open the wallet.

When the fraudster went sentenced, his Bitcoin collection would have been worth a fraction of the current value. The price of this cryptocurrency has seen a sharp rise over the past year, hitting a record high of $42,000 in January. It was trading at $37,577 on Friday, according to cryptocurrency and blockchain website Coindesk.