WATERLOO — Research In Motion is making a $66-million offer to buy Certicom Corp., a Mississauga-based company that specializes in encryption software.

The Waterloo-based company announced the offer Wednesday. It said it plans to offer $1.50 a share for all of Certicom’s outstanding shares.

RIM, which uses Certicom’s software in its BlackBerry wireless communications devices, said it started talking to Certicom’s management in February to evaluate the possibility of a transaction.

“RIM has conducted certain due diligence on the business and we continue to believe Certicom is a natural fit for RIM,” Jim Balsillie, RIM’s co-chief executive officer said in a statement.

The offer was announced less than 12 hours after RIM warned that its third-quarter sales and profits will  be lower than expected due to the weak U.S. economy and the strong U.S. dollar. RIM will report its third-quarter results on Dec. 18.