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BlackBerry, which has persisted in selling smartphones with hardware keyboards, has filed a patent infringement suit against Typo Products, which makes an iPhone case with a built-in keyboard.

Typo's $99 case, which is debuting at the CES conference next week, slips around an iPhone 5 or 5S and connects to it wirelessly via Bluetooth. It provides a keyboard that looks an awful lot like BlackBerry's, including beveled keys.

BlackBerry, which has steadily lost relevance and revenue with the rise of Android phones and iPhones, decided it was time to sue. Steve Zipperstein, BlackBerry's general counsel, had this statement in a Friday announcement:

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. From the beginning, BlackBerry has always focused on offering an exceptional typing experience that combines a great design with ergonomic excellence. 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.

In a statement, Typo said the lawsuit is baseless: "Although we respect Blackberry and its intellectual property, we believe that BlackBerry's claims against Typo lack merit and we intend to defend the case vigorously. We are excited about our innovative keyboard design, which is the culmination of years of development and research."

Typo was founded by Chief Executive Laurence Hallier and TV personality Ryan Seacrest. The device itself was invented by Chief Technology Officer and designer Ryan Hyde.

Patent infringement suits are costly and can be distracting even for well-established companies. If successful, a plaintiff can halt sales of products through a court's injunction and can extract patent licensing fees. A wave of patent suits has embroiled most players in the mobile market over recent years.

The lawsuit, filed in the US District Court for Northern California, accuses Typo of infringing US patents 7,629,964, 8,162,552, and D685,775. It also accuses the company of willfully misappropriating BlackBerry's trade dress -- the distinctive look of the product, and an attribute protected similarly to trademarks.

screenshot by Stephen Shankland/CNET

BlackBerry's design patent D685,775, from 2013, covers the look of its keyboard and is titled "Handheld Electronic Device." Patent 7,629,964, awarded 2009, is titled "Hand- Held Electronic Device With A Keyboard Optimized For Use With The Thumbs." Patent 8,162,552, from 2012, is titled "Ramped-Key Keyboard for a Handheld Mobile Communication Device."

"BlackBerry's innovations in keyboard design have given rise to broad intellectual property rights, including design patents, utility patents, and trade dress protection," the suit said. "Instead of developing its own keyboard design, Typo chose to copy BlackBerry's iconic keyboard design as embodied in, among others, BlackBerry's Q10 smartphone, seeking to trade on BlackBerry's commercial recognition and goodwill."

The suit argues that consumers seeing the products would think they were buying a BlackBerry product: "Typo has misappropriated BlackBerry's patented design in the accused Typo Keyboard. An ordinary observer viewing the Typo Keyboard in the purchasing context would be deceived by its similarity to the D'775 patent design, and would be induced to purchase the Typo Keyboard believing it was the same design as BlackBerry's D'775 patent," the lawsuit said.

Updated 1:49 p.m. PT with details from the lawsuit.

BlackBerry vs Typo Patent Suit Main Filing