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.'"
Wow, what an interesting way to force innovation at such a "minor" expense to the people their efforts are supposed to help. Kinda ironic their efforts have done the exact opposite of their goals... and if the past is any indication, the harm they may have just caused will be around for a while.
If he can do it, so can the bad guys.
What the operators really want is something secure enough so you can't practically listen to a politician's conversations, but open enough so the state can listen to any citizen's conversation. All in the same of National Security. We will only be secure when the reverse is true.
"To those who are overly cautious, everything is impossible. "
We allow people to fear-monger by saying that this can allow criminals to decrypt calls more easily, but, if a couple of dozen hackers at a conference can piece this together through brute-force-ish tactics, are we sure that others haven't already? That's the point that they've made, a point entirely lost in the article.
This does *next-to-nothing* to make the system less secure. It was insecure to begin with. Regulations rendering the dissemination of code-breaking and system-compromising codes and techniques illegal aren't there to protect our data security. They're there to allow companies to use inadequate security measures without public shame.
Of course, this is Slashdot. Anyone who doesn't already know that security through obscurity is ridiculous is an idiot (or a troll). Anyone who relates cryptographic security to fake-rock-key-hiding and calls that rock obscurity (inevitable in a story like this) is just a troll.
If he can do it, so can the bad guys.
And the bad guys aren't going to publish the how-to at a conference.
I am become
worked independently to generate the necessary volume of random combinations until they reproduced the G.S.M. algorithm’s code book — a vast log of binary codes that could theoretically be used to decipher G.S.M. phone calls.
Wait, so just having the encoding algorithm is enough to decipher a message? That's kindergarten cryptography, not something designed for the real world.
The group said that hackers intent on illegal eavesdropping would need a radio receiver system and signal processing software to process raw radio data, much of which is copyrighted.
Yes, that's right. Their main weapon in defending your privacy against crackers who don't care about the law at all is copyright.
operators, by simply modifying the existing algorithm, could thwart any unintended surveillance.
If that's not security through obscurity, I don't know what is.
"To do this while supposedly being concerned about privacy is beyond me"
can someone point me to the article where the GSM Association was outraged when it learned of the illegal wiretapping program which the carriers happily participated in as agents of the u.s. government? i'm sure they protested that, right? riiight?
called Mr. Nohl's efforts illegal
So? What has that to do with whether or not he actually did what he says he did? It's not even worth mentioning. A good encryption system should not depend upon the presumed illegality of breaking it.
says Claire Cranton, a GSM spokeswoman, noting that no one else had broken the code since its adoption.
That you know of, lady. If this guy really has cracked it, odds are someone else has sometime in the past two decades, but wasn't kind enough to so inform you.
The higher the technology, the sharper that two-edged sword.
If that's not security through obscurity, I don't know what is.
Technically, it's insecurity through stupidity.
The higher the technology, the sharper that two-edged sword.
It has been known for a while that GSM can be hacked and that it can be done with a relatively trivial amount of readily available hardware. If you wanted to do it, you could do it. The current effort is mostly a public awareness thing and an ongoing optimization of the attack. People are not going to buy multiple software defined radio boards, tune them with an improved clock source, download or create terabytes of rainbow tables and put it all together just to listen in on their neighbors (which everybody knows would be illegal). People who go to these lengths with anything but research in mind do not need this kind of public "guide" to GSM cracking. GSM is not safe. It hasn't been for quite a while and now people know it. (Two more talks on GSM issues are on the Tuesday schedule. Apparently there are a lot of facepalm type of bugs which are undiscovered purely due to lack of attention.)
'This is theoretically possible but practically unlikely,' says Claire Cranton, a GSM spokeswoman, [...] 'To do this while supposedly being concerned about privacy is beyond me.'
What? Come again?
If Ms. Cranton doesn't even know the argument for full disclosure, why is she the person speaking on behalf of the GSM Association?
Now, we can discuss among ourselves when full disclosure is better than limited disclosure and vice versa, but at least we understand both positions. She doesn't?
Also, if the attack is practically unlikely, why the big concern about privacy? Didn't Ms. Cranton just say this wasn't a big problem, yet at the same time shame Nohl for causing a big problem?
Simon Bransfield-Garth, the chief executive of Cellcrypt, says Nohl's efforts combined with inadequate security designed into the damn thing could put sophisticated mobile interception technology [in the hands of outlaws].
Fixed that for Mr. Bransfield-Garth. The system isn't weak because of Nohl's deeds or misdeeds. It's weak because it's poorly designed. I have seen telecoms security protocols. Only banks have protocols worse than these :(
You shouldn't use words like thence if you don't know what they mean.
Since its been going on for 21years u might figure out if HE DOESNT PUBLISH, MOST BAD GUYS WILL DO IT FOREVER.
Security through obscurity vs full disclosure.
Full disclosure always win for the customer, regular citizens and the greater good.
Obscurity always wins for the bad guys, companies who make money and governments.
ITS AS SIMPLE AS THAT
Obscurity has a unfairly bad rap.
There are two different meanings of obscurity in use in computing these days: one is a standard based on a secret that can be theoretically reverse-engineered; and the other is the non-standard implementation of a standard.
The first, which is what GSM was, is really a "secret algorithm" approach. People call it "obscure" because it could be reverse engineered, but it really was based on keeping a secret from the people who all shared it. It violated Kerckhoff's principle which means it could be exposed, and now it has been. But it took 3.5 billion people 22 years to figure it out, which means that it was a pretty effective secret. That sounds a lot more effective than just plain "obscurity."
Useful obscurity is all about misdirection. It's an opaque curtain, or a mirror, or a fog; it's not an armored wall. Simply configuring your web server to report its identity as IIS when it's really running Apache won't confuse the humans viewing your pages, but it could make an automated attack fail that's based on attacking Apache servers. Changing default port numbers, or default security settings, or reported version numbers, or really shifting anything from the default to a place where it won't be expected by an automated attack is highly effective at keeping the port scanners and script kiddies at bay.
Consider the attack vectors on the internet. Bots and automated scanners make up the vast majority of threats out there. You can't swing a null modem without hitting some zombie that's probing your web server looking for default PHP weaknesses. Obscurity lets you dodge these clumsy attacks for free, and lets you focus your resources on other measures to more effectively improve your security -- IDPs, monitors, etc.
When used properly, obscurity is a wonderful tool that can make your life much easier. It doesn't provide security by itself, but adds another layer that does make you "more secure" overall by removing you from the first waves of automated attacks, giving you time to patch your systems.
John
In addition, they "didn't roll their own" and shouldn't have "just used AES". KASUMI was designed by the Security Algorithms Group of Experts, part of the European counterpart to NIST.
No. In 22 years only one person in 3.5 billion cracked GSM encryption and published his findings. According to the article others have cracked the encryption but haven't published.
What we now know is that it's crackable based purely on data analysis. That tells us everything worth knowing about GSM encryption. Anyone with a need for secure communications now has to treat GSM encryption as if it has been cracked by everyone they want to secure the communications against. To do otherwise would be about the only thing worse than security through obscurity.
Security through obscurity vs full disclosure. Full disclosure always win for the customer, regular citizens and the greater good.
...writes Anonymous Coward.
If anyone wants actual security on a phone, the phones should encrypt end-to-end so that the carrier doesn't know the phone call. The difficulty here is getting a certificate system in place. But there are several viable solutions to that.