Canadian smartphone maker BlackBerry is suing a startup called Typo for infringing on its patents in the latter's signature product, a cellphone case that attaches to an iPhone to give it a physical keyboard.

Waterloo, Ont.-based BlackBerry has filed suit against Typo Products LLC, founded by entrepreneur Laurence Hallier and TV host and media personality Ryan Seacrest for the company's product, the Typo Keyboard, which is set to go on sale later this month.

The device attaches around the outside of an Apple iPhone like a protective case, but gives the device a physical keyboard.

"This is a blatant infringement against BlackBerry's iconic keyboard, and we will vigorously protect our intellectual property against any company that attempts to copy our unique design," BlackBerry chief legal officer Steve Zipperstein said in a release. "We are flattered by the desire to graft our keyboard onto other smartphones, but we will not tolerate such activity without fair compensation for using our intellectual property and our technological innovations."

For years, one of BlackBerry's key differentiators for its smartphones was the ability to have a physical keyboard, which is perceived by some heavy users in the business community to be preferable for writing a lot of text, such as in an email. 

BlackBerry has moved toward touchscreen models in its new phones but does still offer its signature physical keyboard on some of its devices.

More to come