A Texas man admitted Monday to running a bitcoin Ponzi scheme, which at one time controlled about 7% of digital currency in circulation, in what authorities described as the first such federal criminal securities fraud case.

Trendon T. Shavers, who went online by the name “pirateat40,” pleaded guilty Monday in Manhattan federal court to a charge of securities fraud. Under the plea agreement, a second charge of wire fraud would be dropped.

The 33-year-old, who was released on bail, is scheduled to be sentenced on Feb. 3.

His lawyer couldn’t immediately be reached for comment Monday afternoon.

The authorities charged Mr. Shavers had raised more than 764,000 bitcoins through Bitcoin Savings & Trust, a site he founded and ran out of his home. Mr. Shavers, who ran the scheme for about a year through September 2012, personally guaranteed to cover any losses in the event of a market change, according to court documents.