“But moving systems to a smartphone or other mobile device that has built-in computing power that could be used to run algorithms to break that security could ‘open up a big can of worms,’ 
he said. Although he assumes Hilton and other companies considering this move have taken ‘great care’ to reduce risk, he still worries that the additional attack surface and communication abilities of mobile devices might make them more difficult to secure.”
At least one app for the Apple Watch will allow the wearer to unlock a hotel room with the wave of a wrist. But using mobile devices to provide keyless entry to hotel rooms isn’t a novel concept — and could come with added security risks.
Hotels have been experimenting with mobile apps to unlock hotel rooms for some time. The Starwood Hotel group, which is reportedly working on an Apple Watch app, had been testing a similar feature for smartphone users at least since earlier this year. And in July, Hilton Hotels announced guests would be able to use digital check-in and room selection at more than 4,000 properties around the world by the end of this year.
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