Smith was Cincinnati's sixth-round pick. He started 44 games at Fresno State and had 15 interceptions.
Receiver Mario Alford of West Virginia - Cincinnati's seventh-round pick - also has signed a contract.
The Bengals' most intriguing signing so far is former Ohio State quarterback Terrelle Pryor, who attended a rookie camp last weekend on a tryout basis and got a deal after impressing the coaches. He'll have a chance to compete for a job backing up Andy Dalton.
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