Researcher finds major encryption flaw in older mobile SIM cards

Hundreds of millions of mobile handsets using older SIM cards are vulnerable to a flaw that allows attackers to gain complete control over affected handsets, German security expert Karsten Nohl has reported.

What Nohl has spent two years researching could turn out to be the most significant flaw in SIMs in many years when he reveals its full details at a presentation scheduled for the Black Hat security conference at the end of this month.

Nohl's briefings to the media and short website description have so far been light on detail, but the teasers he has been willing to put out sound alarming enough.

According to the Security Research Labs chief scientist, a quarter of 1,000 SIMs tested by his team had proved vulnerable to a weakness in the older DES (Data Encryption Standard) encryption used to secure them.

This made it possible to take control of a handset using a binary SMS text message to upload malware. This piggybacked on the carrier over-the-air (OTA) process through which SIMs are transparently updated via the JavaCard programming interface.

Attackers could use the method to eavesdrop on calls, sent premium text messages, and even in some circumstances, conduct payment fraud.

Only a proportion of the world's handsets used DES in its vulnerable form but this still amounted to 750 million, overwhelmingly older handsets, he said. Not all SIMs using DES seemed to have the flaw, but enough batches to cause major concern.

The size of the issue could define its seriousness with carriers unsure about Nohl's estimates. Most SIMs from recent years would use a different standard, Triple DES (3DES), and be immune to the attack.

The research had been sent to the GSM Association so it could be passed on to carriers, Nohl told media outlets.

"Cards need to use state-of-art cryptography with sufficiently long keys, should not disclose signed plaintexts to attackers, and must implement secure Java virtual machines," he wrote in a blog. "While some cards already come close to this objective, the years needed to replace vulnerable legacy cards warrant supplementary defenses."

Nohl has form when it comes to sniffing out mobile handset issues. Between 2009 and 2011 he publicised a number of security flaws in the GSM standard, most famously in its A5/1 encryption cipher, which could allow call interception between the handset and the network base station.

Cryptocat encryption app maker apologizes, swats bug

The founder of an eavesdropping-resistant instant messaging application called Cryptocat has apologized over a now-fixed bug that made some types of messages more vulnerable to snooping.

Cryptocat, which runs inside a web browser, is an open-source application intended to provide users with a high degree of security by using encryption to scramble messages. But Cryptocat warns that users should still be very cautious with communications and not to trust their life with the application.

The vulnerability, found by Steve Thomas, affected group chats and not private conversations, said Nadim Kobeissi, in an interview from Germany Friday. The encryption keys used to encode those conversations were too short, which in theory made it easier for an attacker to decrypt and read conversations.

The error was the result of an oversight spotted by Thomas, Kobeissi said. The encrypted conversations were still carried over SSL (Secure Sockets Layers), another overlay of encryption. But if an attacker broke the SSL encryption and had the underlying encrypted chats, "it would be significantly easier to crack" using brute-force techniques, he said.

The bug was fixed in Cryptocat versions 2.0 and up about a month ago after Thomas notified the project. The vulnerability persisted for about seven months between September 2012 and April.

Although Cryptocat noted the patch in its changelog, Kobeissi wrote a detailed blog post on July 4 explaining the issue after Thomas published a sharp critique.

"This is a really difficult situation," Kobeissi said. "I am not a person who will gloss over this kind of bug for absolutely no reason just to maintain the image of the project."

The bug was completely unacceptable, but it is common for errors to be revealed in open-source projects, he said. Kobeissi said he gave Thomas a $250 reward out of his own pocket even though Cryptocat has no formal bug bounty program.

"I wanted to be on the record that he was paid for his effort," Kobeissi said.

Cryptocat has seen surging interest since the U.S. National Security Agency's surveillance program was detailed by whistleblower Edward Snowden. Kobeissi said Cryptocat saw 65,000 new users in just a month since the revelations were published. (See also "How to protect your PC from Prism.")

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Encryption can’t protect your data while you’re logged in

You carry a lot of data and sensitive information on your laptop, tablet, and smartphone. The standard method of protecting that information from prying eyes is to encrypt it, rendering the data inaccessible. But with most encryption software, that information becomes accessible the moment you log in to the device as a matter of convenience.

Think about what information that might be: names, postal and email addresses, and phone numbers for friends, family, clients, and business associates; calendar events indicating where you’ll be and when you’ll be there; personal photographs; and more. You might also have proprietary information about your company, clients, information that companies have entrusted you under the terms of non-disclosure agreements, and other sensitive information that should be secured.

Encrypting data protects it from unauthorized access.

Encryption basically scrambles the data so it’s nothing but unusable gibberish to anyone who isn’t authorized to access or view it.

And that’s great, but ask yourself this: How many steps must you go through to decrypt your data? Encryption is designed to protect data, but it should also be seamlessly accessible to the user—it should automatically decrypt, so you don’t have to jump through hoops to use your own encrypted data. And that means it’s not protected at all if someone finds your laptop, smartphone, or tablet in a state that doesn’t require a log-in password.

The Department of Justice and the National Security Administration—the same NSA that allegedly has omnipotent access to all data everywhere—have expressed frustration over iOS 6 and declared its encryption to be virtually impenetrable. There is a way to bypass it, but only Apple knows the magic trick, and there’s a massive backlog of requests from law enforcement.

Remote lock and wipe capabilities are no security or privacy panacea.

There is also a general layer of encryption in iOS that functions purely as a means of remotely wiping the device running it. Rather than literally erasing all of the data—which would take a little time depending on how much data there is—this remote wipe tool simply resets the encryption key, instantly rendering the data useless. That’s handy, but it’s not foolproof.

iOS devices also have hardware-based encryption that protects your data, including your email and its attachments. That encryption, however, is tied to a passcode, meaning you must actually assign and use a passcode for your iOS device in order for your data to be protected.

The BitLocker encryption in Microsoft Windows works along the same lines. The TPM (Trusted Platform Module) chip provides a hardware-based element, and the user login provides the key to unlock the encryption and make the data available to the user.

All popular encryption tools lock data from unauthorized access, but are designed to unlock when a user successfully logs in. The data is then available as if it weren’t encrypted at all, and the user doesn’t have to take any additional steps to access or use the encrypted information.

Can you see the problem with this approach? This feature designed to make encryption more convenient renders the data protection impotent as long as you’re logged in.

Tripwire Director of Security Operations Andrew Storms explains, “If a thief catches your device in an unlocked state, they have a potential window of opportunity to access the data stored on that device.”

The best way to secure data is to configure your mobile devices to require passcodes after short periods of nonuse.

That “virtually impenetrable” iOS encryption relies on your device being locked with a passcode. When you set a passcode in iOS, you can choose whether the device should require the passcode immediately, or in one minute, five minutes, 15 minutes, or even an hour. An hour! If you choose that setting, you’re basically leaving your “encrypted” data exposed to potential compromise for 60 minutes.

The best way to secure the data on your mobile device is thus to configure the device to require a passcode after a relatively short period of nonuse. Set the time limit too short, and you’ll find yourself becoming irritated by repeatedly having to retype your passcode. Leave it unlocked for too long and you give a thief plenty of time to access all your supposedly encrypted data.

According to Tripwire CTO Dwayne Melancon, “In an enterprise environment, a lot of these complementary policies can be driven using group policies—for example, requiring screen locking, passwords upon waking, and setting short timeouts for automatic locking and automatic locking when the lid of a laptop is closed.”

While iOS and other mobile devices—as well as many other encryption tools—provide the ability to remotely lock or wipe the data from a device, that tool is useful only if you realize the device is gone. Every second your laptop, tablet, or smartphone remains unlocked while it’s out of your control is time that your encryption is not doing anything to protect your data.

Tripwire’s Storms points out that remote lock and wipe capabilities are no panacea: “On mobile devices, a clever thief will immediately disable all network access, so the device is unable to receive that remove lock or kill switch signal from corporate administrators.”

A better alternative to timed lockouts might be to have some sort of Bluetooth, NFC (near-field communication), or other close-proximity wireless device that pairs with your laptop, tablet, or smartphone. Keep this device on your person, and if you move too far away, your mobile device will automatically lock to prevent unauthorized access.