Leading cryptocurrency exchange Bitfinex is offering a reward of up to $400 million for the return of bitcoin stolen from the exchange in a hack in 2016.

The hack involved the theft of 119,756 bitcoin worth $65.6 million at the time but today worth $1.335 billion. The company later socialized the loss, deducting 36% of the bitcoin balances of its customers to cover the loss and issuing a new token called BFX that had a theoretical value equal to the amount each customer lost as compensation.

Under the offer, any person who puts Bitfinex in contact with the hacker behind the theft will receive 5% of the total property recovered, while the hackers will receive 25% of the stolen bitcoin should they return the bitcoin they stole.

“In order to confirm the identity of the hackers, we will request that 1 Satoshi is sent from the wallet address responsible for the hack to a wallet address specified by Bitfinex,” the company said in a blog post. “We will work to ensure this can be done safely, thereby protecting the identities of all parties and Bitfinex reserves the right to impose conditions on any transfers in order to verify claims and ensure a secure process.”

To date, about 27 bitcoin has been recovered from the hack, but most of the stolen funds have never been moved. Bitcoin Exchange Guide reported that the first time the hacker moved stolen funds was in April 2019, with 300 bitcoin transferred to 13 new addresses. A further 29 bitcoin was moved in May and $12 million more was moved in July and early August.

Bitfinix has certainly had its ups and downs over the years since the hacking, including being sued for dipping into reserve funds for its Tether stable coin, but it has powered ahead. The exchange raised $1 billion in an “initial exchange offering” in 10 days in May 2019 from an unspecified number of large investors who were said to include “giants in our industry.”

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