MISSISSAUGA, Ont. - Certicom Corp. (TSX:CIC) fired yet another shot Monday in its struggle to fend off a hostile takeover by tech heavyweight Research in Motion Ltd. (TSX:RIM), issuing an official rejection of the $66-million offer.

"After a thorough review involving both the special committee of independent directors and its financial and legal advisers, the board found the RIM bid to be significantly undervalued, opportunistic and not in the best interests of Certicom shareholders," Certicom said in a statement.

The announcement came as no surprise, the Toronto-area data encryption company having already frowned upon the bid in a preliminary statement.

It recommended Monday that shareholders not tender to the bid.

"Among other things, the board found that, at $1.50 per share, the RIM offer does not provide fair value for Certicom's cash on hand and the significant potential tax assets that could be available to a taxable Canadian corporation - such as RIM," the company said.

"Further, RIM's hostile bid undervalues both Certicom's valuable and unique industry-leading data encryption technology and the recent progress the Company has made in implementing its strategic plan."

Earlier in the day, Certicom said it has gone to court to block RIM from making the hostile bid, arguing the BlackBerry maker's offer violates confidentiality agreements between the two companies.

Certicom has counted Research in Motion as a customer for many years, and said the bid contravenes non-disclosure agreements signed in 2007 and 2008.

"Access to this information also provided RIM with a significant information and timing advantage relative to other parties that may have an interest in entering into an alternative transaction with Certicom," the company said in a statement Monday.

On Thursday, Certicom called RIM's hostile takeover offer of $1.50 per share or $66 million "highly opportunistic" and that it undervalues the Mississauga, Ontario-based company.

Certicom's special committee of independent directors urged shareholders to take no action regarding the offer.

In a statement released early Monday, RIM said it had been told that Certicom planned to apply to Ontario Superior Court and the Ontario Securities Commission for an injunction and cease trade order.

Certicom confirmed it had made those applications in a later announcement.

RIM says it intends to "vigorously oppose" Certicom's applications.

Jim Balsillie, co-CEO of RIM, has said the BlackBerry maker has been talking to Certicom's management about a potential transaction since February 2007.