A takeover battle is brewing over Certicom Corp after the encryption software vendor’s executive today gave a nod of approval to a revised $107 million offer tabled by Blackberry maker RIM Ltd to outbid Verisign Inc.

Certicom has said it considers the offer a ‘superior proposal’ but that it has to entertain further interests from Verisign, if it were to amend the terms of its last offer. 

Ontario-based Certicom had last month agreed to a $73m all-cash takeover by VeriSign, in a deal that came with a 40% premium on a hostile bid launched by RIM in December. 

RIM has countered that and come back with a cash offer that is 43% more than the price mooted by VeriSign.

The deal comes weeks after Certicom won a court battle against RIM over its first unsolicited bid.

Certicom provides wireless security software to a long list of technology vendors that include IBM, Motorola and Texas Instruments, but its encryption programmes are seen as being absolutely critical to the future development of secure messaging on Blackberry devices.