Last week, The Intercept reported that the NSA had been able to capture and store the encryption keys that protect SIM cards. Now, Gemalto—the largest SIM card manufacturer on the planet—has responded, denying the breach and explaining that 3G and 4G networks are unaffected.

The reports from last week claimed that the NSA and Britain's equivalent, GCHQ, has been able to decrypt cell phone signals in mid-air or remotely implant malware on hardware to grab SIM encryption keys on any phone using a Gemalto SIM card. That was a big deal, because Gemalto churns out a staggering 2 billion SIM cards every year for over 450 carriers—including AT&T, Sprint, and Verizon. Holding the encryption keys to them would have huge, global privacy ramifications.

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Today, though, Gemalto has issued a press release explaining that while it has "reasonable grounds to believe that an operation by NSA and GCHQ probably happened," it is confident that the attack "only breached its office networks and could not have resulted in a massive theft of SIM encryption keys." Indeed, Gemalto claims that the attempts to intercept encryption keys occurred as they were exchanged between mobile operators and their suppliers globally starting in 2010, by which time it had "widely deployed a secure transfer system with its customers and only rare exceptions to this scheme could have led to theft."

"It is extremely difficult to remotely attack a large number of SIM cards on an individual basis," exlplains Gemalto. "This fact, combined with the complex architecture of our networks explains why the intelligence services instead, chose to target the data as it was transmitted between suppliers and mobile operators." Gemalto also seeks to reassure, explaining that even if those encryption keys were stolen, they'd only be of use to spy on communications on second generation 2G mobile. "3G and 4G networks are not vulnerable to this type of attack," it explains.

The Intercept's report from last week claimed that SIM attacks were later levelled at countries including Afghanistan, Yemen, India, Serbia, Iran, Iceland, Somalia, Pakistan and Tajikistan by security agencies. The attack didn't always work—in Pakistan, for instance—and Gemalto points out that those failures occurred where operators had begun to use Gemalto's secure exchange process. It also adds that the secure process was available for any operator to use, but notes that "certain operators and suppliers had opted not to use them."

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All of which is a fairly long-winded way of explaining that the blame doesn't perhaps lie squarely at the feet of Gemalto or other SIM suppliers. Indeed, only two percent of the 1,719 exchanges of encryption keys listed in the documents described by The Intercept came from SIM suppliers. The rest came from elsewhere.

Image via Flickr / Simon Yeo