By Patrick Marshall

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PHADE phone alert (Purdue Simba Lab/YouTube)

What happens when surveillance cameras can connect with your smartphone?

You’re about to cross a downtown street and your smartphone beeps to tell you that a text message has arrived.  As you pull out your phone to check the message as you walk, the phone receives an alert from your local police — you’re about to step into the path of a rapidly approaching SUV!

Such a scenario may become possible with a technology called PHADE that allows public surveillance cameras to send personalized messages to people without knowing the address of the phone.

Developed by researchers at Purdue University, PHADE digitally associates people in the camera's view with their smartphones by using the subjects' behavioral address, or the identifiers extracted from their movements in the video.

While traditional communications require an IP address or a media access control (MAC) address to deliver messages to the right device, PHADE employs a unique method of matching messages to recipients.  With PHADE, a video stream tracks the movements of people within range, then analyzes and encodes those movements as an “address.” At the same time, an application on a subject’s smartphone is doing the same analysis using the phone’s sensors.  When PHADE broadcasts a message it will be received only by the smartphone that has a matching “address.” 

Even better, said He Wang, assistant professor of computer science, the system doesn’t violate individuals’ privacy.

After encoding a user’s movements to create an address, PHADE “blurs” the data to prevent it from being used to identity the person. Plus, it allows the personal sensing data to remain on subjects' phones instead of asking them to upload the data to server.

The technology can be used by governments to enhance public safety. "For example, the government can deploy cameras in high-crime or high-accident areas and warn specific users about potential threats, such as suspicious followers,” fellow researcher Ph.D. student Siyuan Cao said.

In addition to deploying PHADE for public safety, the Purdue team suggested that the technology might also be used to provide tailored information to visitors at museums or historical sites.

Still, there’s something unsettling about a communications system that watches our movements and sends messages based on what we are doing. Yes, it may save us from being run over by an approaching car, but it may also pester us with advertisements as we walk through a store.

The prospects get even creepier if entities -- whether government agencies or private-sector companies -- combine PHADE with other technologies, such as face-recognition programs and artificial intelligence that can identify a subject's sexual orientation. (Yes, such software exists, according to a 2018 article by Yilun Wang and Michal Kosinki, “Deep Neural Networks Are More Accurate Than Humans at detecting Sexual Orientation From Facial Images,” in the Journal of Personality and Social Psychology.)

It’s true, as Wang said, that PHADE does not violate the privacy of smartphone owners. It does nothing to identify the users or anything about them other than how they move.  But PHADE does offer a unique opportunity for government or companies that license the technology to intrude on individuals. 

How PHADE is used will depend on the types of applications licensees build and whether end users allow those applications on their smartphones, Wang said. “We provide a way to communicate, but how to use it depends on the entities who apply our work.”

Powerful new technologies offer potential for both beneficial uses and for abuse.  Policymakers and end users alike must consider how the increasing capabilities of those computers we carry with us -- chock full of sensors and communications tools we may not even be aware of -- may impact us in some ways we’d rather than not experience.

Posted by Patrick Marshall on Jul 06, 2018 at 1:43 PM


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