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T-Mobile toughens network encryption against government snooping

The older cellular encryption can be cracked by the National Security Agency, leaked documents previously showed. An upgrade to that security could make eavesdropping a lot harder.
Written by Zack Whittaker, Contributor
Image: CNET/CBS Interactive

T-Mobile's networks may have changed for the better — stronger signal, faster speeds, better coverage — but what you probably didn't know is that they're now even more secure.

In upgrading its U.S. networks, the fourth largest cellular giant in the country also bolstered encryption in a number of cities, switching to A5/3 encryption from the A5/1 standard on the older 2G networks, which in some cases still carry calls or text messages when faster data isn't available. Newer technologies, like 3G and 4G (LTE), already offer significantly stronger encryption.

The Washington Post, which first tested the networks in a number of cities, said New York, Washington, and Boulder, Colorado are now using the newer standard, covering tens of millions of customers.

Upgrading the network to the newer A5/3 encryption makes it significantly harder to eavesdrop on calls and text messages. Even for the National Security Agency, which reportedly is able to decode the older, legacy A5/1 encryption, may face headaches with the new standard.

T-Mobile did not comment on the encryption.

In densely populated areas, such as the cities with enhanced encryption, monitoring cellular calls becomes more difficult — simply because of the volume of people. The call and text data is still routed through ground networks, but filtering it becomes difficult. The Post explained that an "IMSI catcher," which can identify an individual cell subscriber, can make it easier to snoop on calls and texts without having to crack the phone or network's encryption.

AT&T said it is already ramping up its encryption efforts by offering A5/3 encryption, but tests by the Post found  in U.S. locations where T-Mobile upgraded, AT&T had not.

In any case, AT&T is shutting down its A5/1-encrypted 2G network by 2017, and replacing it with newer technology.

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