BALTIMORE (AP) -- A Utah man pleaded guilty to a drug conspiracy charge Thursday for his role in an online black market known as the Silk Road that authorities say processed more than $1 billion worth of illicit business.

The guilty plea from Curtis Clark Green, 47, comes one month after federal authorities shut down the drug-dealing website, which conducted business with tough-to-track digital currency and sought to protect the anonymity of its users by operating on an encrypted network.

Green, whose lawyer identified the defendant as being from Spanish Fork, Utah, declined to comment after the plea hearing. His attorney also declined comment. Dressed in a white shirt and tie, and gripping a cane as he entered the courtroom, Green answered standard 'yes' or 'no' questions from the judge but made no detailed statement about the allegations.

The website allowed users to anonymously browse through nearly 13,000 listings under categories like "Cannabis," ''Psychedelics" and "Stimulants" before making purchases using Bitcoin, a form of online currency. It offered various illegal services along with drugs, and as of July, had nearly 1 million registered users from around the world, according to court papers.

A so-called hidden site, Silk Road used an online tool to mask the location of its servers and generated an estimated $1.2 billion since it started in 2011, authorities say.

It was shut down when authorities arrested Ross William Ulbricht, a college-educated San Francisco man they allege masterminded the operation while hiding behind the alias of "Dread Pirate Roberts," an apparent reference to a main character in "The Princess Bride," the 1987 comedy film based on a novel of the same name.

He was arrested in a branch of San Francisco's public library, where authorities say he was chatting online with a cooperating witness. Ulbricht, 29, who is also charged in Maryland in a failed murder-for-hire plot, was ordered held after a court appearance this week in New York. His lawyer said that his client is innocent and is not the person who used the "Dread Pirate Roberts" alias.

The investigation was launched in 2011 in Baltimore, where agents from U.S. Immigration and Customs Enforcement's Homeland Security Investigations formed the "Marco Polo" task force — with representatives from other law enforcement agencies — to target Silk Road and its administrators. William Winter, the office's special agent in charge, said in a statement that his agents will continue to pursue crimes committed by users of "networks and digital currency designed to provide anonymity."

Green, who used the aliases of "Flush" and "chronicpain," acknowledged as part of his guilty plea that he served as an administrator for the website. The position gave him access to the details of financial transactions conducted through the black market bazaar and also made him responsible for fielding questions and complaints from buyers and sellers and determining whether law enforcement officials were secretly poking around the site, the authorities said.

Prosecutors say he also served as a middleman between a drug buyer who operated on Silk Road and an undercover agent who posed as a cocaine smuggler able to deal large quantities of the drug.

The agent contacted Ulbricht, who directed Green and other website administrators to find dealers willing to purchase a high volume of drugs, authorities say. Green admitted helping the undercover agent hook up with a particular buyer who was active on the site; the vendor and undercover agent negotiated a cocaine deal for roughly $27,000, and Green agreed to have the package sent to him, according to prosecutors.

He was arrested in January after the one-kilogram package was delivered to his house by an undercover U.S. Postal Service inspector.

He faces up to 40 years in prison at his sentencing in February.

His court appearance followed a similar plea Tuesday from Jacob George IV, an Edgewood, Md., man who admitted selling drugs via Silk Road.