NEW YORK—A Texas man who carried out what authorities said was the first federal bitcoin securities fraud to be prosecuted was sentenced on Thursday to 18 months in prison.

Trendon Shavers, 33 years old, was sentenced in Manhattan federal court by Judge Lewis A. Kaplan, who said Mr. Shavers committed a serious crime but had earned leniency through the honest work he has done since his 2014 arrest. Federal sentencing guidelines had called for a prison term of nearly three years.

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