Coinbase, the largest cryptocurrency exchange based in the U.S., said Thursday that criminals had improperly obtained personal data on the exchange’s customers for use in crypto-stealing scams and were demanding a $20 million payment not to publicly release the info.

Crypto giant Coinbase has confirmed its systems have been breached and customer data, including government-issued identity documents, were stolen.

Coinbase Global said an unknown party has stolen customer data and is demanding money in exchange for not publicly disclosing the information.