Hackers have stolen sensitive customer data from crypto exchange Coinbase and are demanding a ransom of $20 million (17.9 million euros). The largest American trading platform for cryptocurrencies says it will not pay the ransom.

Coinbase reports that criminals have bribed customer service employees to provide data such as names, addresses and copies of IDs.

The hackers used this data to approach customers and pose as Coinbase employees. They tried to convince customers to transfer their crypto coins.

The attackers were supposed to keep their action quiet if Coinbase paid the ransom, but the company refuses to do so. However, the crypto exchange has promised to compensate customers who have lost their crypto coins. According to the company, this concerns less than 1 percent of the monthly active users.

The announcement of the hack has cost Coinbase dearly: the company’s share price fell by more than 4 percent. Coinbase is offering a $2 million reward for the golden tip that leads to the arrest of the criminals responsible.

Coinbase acquired the Dutch digital currency company Deribit last week. The acquisition involved around 2.6 billion euros.