SIM Cards Have Finally Been Hacked, and the Flaw Could Affect Millions of Phones

SIM Cards Have Finally Been Hacked, and the Flaw Could Affect Millions of Phones
forbes.com

Here, for us, are the nut grafs:

In early 2011, Nohl’s team started toying with the OTA protocol and noticed that when they used it to send commands to several SIM cards, some would refuse the command due to an incorrect cryptographic signature, while a few of those would also put a cryptographic signature on this error message.

With that signature and using a well known cryptographic method called rainbow tables, Nohl was able to crack the encryption key on the SIM card in about one minute. Carriers use this key to remotely program a SIM, and it is unique to each card.

This is a little vague and I don't understand the OTA protocol like, at all, but what it sounds like is that there is a case in some implementations of SIM OTA where (a) errors for improperly signed messages are noisy, (b) those errors include some of the plaintext of the improperly signed message, and (c) the error message itself has a signature that is intended to be valid only for the error.

Possible next steps: (i) you can table-solve for the signature (presumably this is a MAC, not a signature) for your intended message due to the way plaintext hits the error message, or (ii) you can table-solve for the plaintext of a previously unknown ciphertext by taking that ciphertext, flipping a bit to invalidate the signature, and collecting the error signature.

     *Verizon did not specify why its SIMs were not vulnerable*

But seriously, there is a sunny side to this story: a user could load her own programs onto her SIM. She could gretaly extend the functionality of her phone... with programs that she trusts. Maybe even ones she wrote herself.

Imagine... an open platform. Oh gosh, that would be terrible, wouldn't it?

Otherwise this story highlights the concept of "minimum viable product" not in the startup world, but as it exists among major industry manufacturers. For example, if SIM manufacturers can get away with using DES, then why invest their time and money in using stronger crypto? There are so many examples of this type of thinking... it's certainly not limited to imlementations of cryptography or SIM cards. No doubt, some would say this is simply Business 101... ask any used car salesman. But it's particularly acute in hardware and software.

Do hardware and software worlds makers need higher standards and more serious "quality control"? Beyond the cosmetic appearance of their work, no. Because users are generally indifferent to all else. What they don't know won't hurt them.

Did you know you can type encrypted messages directly with a text editor called ed(1)? How cool is that? It's so easy. Who needs PGP?

It uses DES, but hey, DES is good enough for SIM cards, so...