A patent lawsuit by BlackBerry Ltd. on Friday shows that while its market share may have slumped to below 2%, it remains a zealous protector of what has long been one of its best-known assets: its keyboard.

The target of the litigation is Typo Products LLC, the maker of a snap-on keyboard accessory for the iPhone, which received some buzz last year thanks to investment from its celebrity co-founder, TV host Ryan Seacrest. The $99 Typo keyboard is set to go on sale this month.

BlackBerry's general counsel, Steve Zipperstein, called the Typo "blatant infringement against BlackBerry's iconic keyboard," saying the company "will vigorously protect our intellectual property against any company that attempts to copy our unique design."

"We believe that Blackberry's claims against Typo lack merit and we intend to defend the case vigorously," Typo said in a statement. In an interview Friday, Typo CEO Laurence Hallier rejected the claims, and said they would not affect the company's plans to begin shipping devices this month. "We checked out the patents," he said. "We have been working on this keyboard for two years. We developed this from the ground up."

It is unclear exactly which patents Typo is alleged to have violated, and BlackBerry declined to discuss the lawsuit beyond a news release. The suit was filed in the U.S. District Court for the Northern District of California.