A Bitcoin exchange operator who pled guilty to supplying $1 million in digital currency to people buying drugs on Silk Road was sentenced to four years in prison Tuesday.

Robert Faiella, who used the name BTCking online, had been arrested last year and charged with conspiracy to commit money laundering and operating an unlicensed money transmitting business. He had been charged along with Charlie Shrem, former CEO of the Bitcoin exchanger BitInstant. Shrem was sentenced last month to two years in prison.

According to court documents, from December 2011 until October 2013 when Silk Road was seized by federal agents, Faiella, 55, operated a Bitcoin exchange on the Silk Road site that allowed drug buyers and sellers to anonymously exchange cash for Bitcoins — the only currency used on the Silk Road site to buy drugs and other paraphernalia marketed through the site. Faiella obtained the Bitcoins through BitInstant, then sold them at a profit to Silk Road users.

Authorities say Shrem knew about Faiella’s activities and personally processed his orders, giving Faiella a discount on high-volume trades of Bitcoins that he purchased for Silk Road buyers. Faiella exchanged tens of thousands of Bitcoins a week for Silk Road users until the site was closed by authorities in October 2013.

To purchase Bitcoins for use on Silk Road, Faiella submitted orders to BitInstant specifying the number of Bitcoins he wanted to purchase and provided an email address. A third company, which handled the cash transactions, replied with an email instructing where to deposit the cash. The latter included a handling fee attached to it that was designed to help the company identify each transaction to the proper purchaser.

For example, one handling fee might be .32 cents, another would be .45 cents. Customers would be told to pay $200.32 or $200.45, with no customer being given the same handling fee on the same day so that the company could deposit the Bitcoins into the proper anonymous account.

Customers would then deposit the cash in person at the specified local bank, directing the money to a bank account owned by the cash-processing firm. Once the cash deposit was verified, the Bitcoins were transferred to the customer’s Bitcoin account of choice.

Faiella promised in an advertisement for his service that Bitcoins would be deposited so fast that they would likely be in the buyer’s Bitcoin account before they returned from the bank.