Slashdot Mirror
GSM Decryption Published
Hugh Pickens writes "The NY Times reports that German encryption expert Karsten Nohl says that he has deciphered and published the 21-year-old GSM algorithm, the secret code used to encrypt most of the world's digital mobile phone calls, in what he called an attempt to expose weaknesses in the security system used by about 3.5 billion of the 4.3 billion wireless connections across the globe. Others have cracked the A5/1 encryption technology used in GSM before, but their results have remained secret. 'This shows that existing GSM security is inadequate,' Nohl told about 600 people attending the Chaos Communication Congress. 'We are trying to push operators to adopt better security measures for mobile phone calls.' The GSM Association, the industry group based in London that devised the algorithm and represents wireless operators, called Mr. Nohl's efforts illegal and said they overstated the security threat to wireless calls. 'This is theoretically possible but practically unlikely,' says Claire Cranton, a GSM spokeswoman, noting that no one else had broken the code since its adoption. 'What he is doing would be illegal in Britain and the United States. To do this while supposedly being concerned about privacy is beyond me.' Simon Bransfield-Garth, the chief executive of Cellcrypt, says Nohl's efforts could put sophisticated mobile interception technology — limited to governments and intelligence agencies — within the reach of any reasonable well-funded criminal organization. 'This will reduce the time to break a GSM call from weeks to hours,' Bransfield-Garth says. 'We expect as this further develops it will be reduced to minutes.'"
encryption is nothing more than security through calculated obscurity.
I think you can only prosecute an argument for that claim successfully if you engage in semantic shifting.
That is to say, you're right only if you take the word `obscurity' to mean something different from what everybody else takes it to mean.
Security by obscurity generally means you're relying on the adversary to be ill-informed about some aspect of the crypto which wouldn't be a problem for him to know about in a "real" cryptosystem, and/or extremely limited in computational power.
For instance, the windows 95 screen saver password (at most 14 characters) was stored in the registry, xor'ed with a fixed key of length 14. Probably a const char screen_saver_xor_pad[14] = [...], "safely" hidden away in some undisclosed source code. Security by obscurity.
This is also how DRM works: encrypt a bit string f with key k, then send k and e_k(f) to the recipient, but sneakily, hoping that the recipient will only decrypt and use f in accordance with the rules your piece of software implements. Security by obscurity.
Take on the other hand AES. Go do an exhaustive key search. If you're smart, do a meet-in-the-middle. That's sqrt(2^n), which is still exponential (it's sqrt(2)^n). Okay, n is fixed, but still: the best attack is (essentially) brute force. That's real security.
Then there's of course the gold-plated but impractical security (well, encryption): whenever you want to send a message m that's b bits long, come up with a uniformly random b-bit key k, then transmit m XOR k. Perfectly secure, but good luck sending k to the recipient. You can pre-share it, though, so if you put 4 TB of random key in your submarine, it can send 4 TB back to HQ confidentially. Or you can do quantum key distribution (if you have the required equipment).
I recommend that while your post has a valid point, you try to refrain from commenting on the more technical aspects of security.
I recommend you try to refrain from assessing peoples' understanding of the technical aspects of security and making recommendations based upon that assessment. I haven't seen anything in your parent's post which suggests they don't understand the subject matter, unless we take your semantic shift to be The Right Way to understand "obscurity."