Between the Lines

Larry Dignan, Andrew Nusca and Rachel King

Code that encrypts world's GSM mobile phone calls is cracked

By | December 28, 2009, 10:21am PST

Summary: A German computer engineer said that he had cracked the secret code used to encrypt most of the world’s mobile phone calls.

A German computer engineer said Monday that he had cracked the secret code used to encrypt most of the world’s mobile phone calls.

In an attempt to expose holes in the security of global wireless systems, 28-year-old Karsten Nohl cracked the 21-year-old GSM algorithm, which is used to encrypt 80 percent of the world’s mobile calls, reports the New York Times.

Nohl revealed his success at the Chaos Communication Congress in Berlin, Germany. He said that 24 people worked independently to reproduce the code book, or binary code log, for the algorithm, which contains the equivalent of about two terabytes of data.

He announced his intentions to crack the GSM algorithm at a conference in August.

[Nohl's wiki page for the A5/1 project]

The GSM Association reportedly said that Nohl’s actions were illegal in the U.S. and U.K., and said it was unlikely that Nohl had actually cracked the code.

Nohl reportedly said the code book is available on the Internet through BitTorrent.

The issue at the center of it all: should wireless carriers and/or the government take more steps to ensure the security of GSM wireless phone calls?

The GSM algorithm is an A5/1 algorithm, a 64-bit binary code now slightly outdated compared to the 128-bit codes used today to encrypt calls on third-generation networks. A successor, called the A5/3 encryption algorithm, was later developed, but most network operators haven’t yet implemented it.

A known encryption expert, Nohl has a PhD. in computer engineering from the University of Virginia.

Earlier this year, he exposed weaknesses in the security algorithm for cordless home phones, prompting the DECT Forum, a standards group, to revisit it (.pdf). Nohl previously studied the security of RFID systems.

About 3.5 billion of the 4.3 billion wireless connections across the globe use GSM. In North America, 299 million consumers use the technology.

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Topics

Andrew J. Nusca is associate editor of ZDNet and editor of SmartPlanet.

Disclosure

Andrew Nusca

Andrew J. Nusca does not hold any investments in the technology companies he covers.

Biography

Andrew Nusca

Editor

Andrew J. Nusca is an associate editor at ZDNet and editor of SmartPlanet. As a journalist based in New York City, he has written for Popular Mechanics and Men's Vogue and his byline has appeared in New York magazine, The Huffington Post, New York Daily News, Editor & Publisher, New York Press and many others. He also writes The Editorialiste, a media criticism blog.

He is a New York University graduate and former news editor and columnist of the Washington Square News. He is a graduate of the Columbia University Graduate School of Journalism. He has been named "Howard Kurtz, Jr." by film critic John Lichman despite having no relation to him. He lives in his native Philadelphia with his wife, cat and Boston Terrier.

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RE: Code that encrypts world's mobile phone calls is cracked
dsfwrryd4801-24353684299829058221678783432078 4th Nov
ryzxrn,good post!
0 Votes
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illegal?
baboddonggae 28th Dec 2009
"The GSM Association reportedly said that Nohl?s actions were illegal in the U.S. and U.K., and said it was unlikely that Nohl had actually cracked the code."

When someone finds a flaw in your security it's better to listen to them than condemn them. What if we just sued everyone who cracked WEP rather than creating WPA(2)? Sounds like a bad idea to me.
0 Votes
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on the Internet, so he should be jailed for that.

Seriouslly, how much different is that then someone who figures out the combo to your shed, then gives that to someone else who promptly steals your tools?

Should something happen, he at least should be an accesorry to the crime.
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Umm no.
Snooki_smoosh_smoosh 28th Dec 2009
He didn't create the exploit, and in fact if
you had read the attached article you would
know that there is already code books available
for about 6 figures.

The point is that there are secure standards
out there, but your providers just drag their
feet at getting them rolled out. 3G Voice for
instance is more secure than A5/1.

And if it hasn't been done already, a crafty
bot net writer could do the same thing Nohl has
done by making the botnet a distributed
computing platform, which is what a botnet
basically is anyway, to compute out the cipher,
in a few days time.
0 Votes
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Your analogy is flawed
Takalok 28th Dec 2009
Still, he said that the codebook was released on the Internet, so he should be jailed for that.

It's more like a bank advertising how secure they are (when they're not) and a reporter discovering that and then reporting it. Your tool shed is private; GSM is public.

He should get a medal and big pat on the back.
0 Votes
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The thing about encryption...
LiquidLearner 28th Dec 2009
is that it's designed with a certain lifetime in mind. As tech advances then the ease with which what was once strong encryption is cracked is accelerated. WPA w/ TKIP is no longer secure as TKIP was designed as an interim encryption solution.

If GSM is unchanged in 21 years it's held up incredibly well but it's time to think about a new encryption scheme.
0 Votes
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so what
Linux Geek 28th Dec 2009
isn't the government tapping the cell phones too....with no hacking required.
0 Votes
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Who do you think invented phones?
jdbukis@... 28th Dec 2009
It was the gummit so they can liez to you hackzor!
0 Votes
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No, it was Microsoft
LiquidLearner 28th Dec 2009
In order to stifle innovation and make an easily hackable communications system. You should know better than anyone else that if it was hacked then cleared it was Microsoft, and probably Vista's fault.
0 Votes
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1
Cylon Centurion 28th Dec 2009
Nt
0 Votes
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Well said...
Wintel BSOD 28th Dec 2009
Couldn't have said it better myself...

lol...
0 Votes
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Sweet!!
rhonin 29th Dec 2009
lmao!!!
0 Votes
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What do you get after you bust the code?
BALTHOR Updated - 28th Dec 2009
Do you get to hear people talking on the phone?The digital stream is probably encrypted at the caller's phone.Whoever the caller calls gets the decryption file.Encryption/decryption is a mathematical scrambling of the digital stream.End computer virus.
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Depends on what he means by "cracked"
andrej770 Updated - 28th Dec 2009
If he cracked the encryption key, then decrypting those phone conversations is easy. But then again, a new key could be issued to the carriers and the cat and mouse game starts. Its funny that the GSM association started off talking saying that what he was doing was illegal - almost saying, even if he did its illegal; which is a no-brainer, but it did not stifle desire to learn more about this. The fact that they deny it, only makes people want to know more about what is possible. The GSM association is in the same boat the music industry was in years ago. They wait for forever to enforce a mandatory implementation of their standard (due to security) and now that hacking attempts are being made they have to rush defend their lack of focus and leadership.
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Doesn't Bother Me
ctunk 28th Dec 2009
I only use my cell for sex party lines mostly with Asian minors so I could care less...........

If not that I may make the occasional phone call requiring me to say or touch my SSN which is not a big deal either if the network is unsecure.

I am sure the government listens to enough cell phone calls already!!!!!!!
0 Votes
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Yes, there really is a rason most providers have not migrated to better encryption, it makes cracking it too hard for the US government.
0 Votes
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Governments do not need the ciphers to get in,
Snooki_smoosh_smoosh 29th Dec 2009
they just listen in at the source. You know that
secret room in the ATT building.
0 Votes
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Last Time I Checked...
Peter Perry 28th Dec 2009
Last Time I checked, the USA had more CDMA Subrscribers than GSM which means it is inaccurate to say that 299 Million (roughly the entire US Population) uses this technology because at best it is 50% but I would bet it is lower than that...

Crud, think of how much of the population can't or won't use technology (1 to say 10 year olds and some people over 65).
0 Votes
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I may be wrong, but...
Rick_K 28th Dec 2009
I believe that US census reported that there were @ 305 million legal
residents in the United States. Then there are those 47 million illegals
that Osama Obama is protecting. I am having a real hard time nailing
down who exactly carries GSM and CDMA. But that is another story, The
most recent figurers came up in 2007, which is consistent with what you
posted. I do not believe that there are even 200 million active cellphones
in the United States. HEre is the part I am thinking. Again I may be
wrong, but I am willing to bet the number quoted includes the
disposable cellphones. Add those in to the mix, and the numbers skew
off into left field.
0 Votes
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More than 1
People 28th Dec 2009
In many cases, one person has more than 1 phone.

I question the 299 million number myself, but I don't think it's outside
the realm of possibility.
0 Votes
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Again read the article or take a
Snooki_smoosh_smoosh 29th Dec 2009
Geography class...
0 Votes
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What a dolt, did you even read the stat
Snooki_smoosh_smoosh 29th Dec 2009
It said NORTH AMERICA, not the USA. North
America includes Canada and Mexico. The US is on
the Continent of North America, as is Canada and
Mexico. Take a geography class.
0 Votes
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3G still safe?
shadowself 29th Dec 2009
"The GSM algorithm is an A5/1 algorithm, a 64-bit binary
code now slightly outdated compared to the 128-bit codes
used today to encrypt calls on third-generation
networks."

This seems to say that any 3G call or data transfer is
still uncracked. So it's only the GSM variant of 2G or
"2.5G" that people need to be concerned about.

Comments?
0 Votes
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Yes for the time being
Snooki_smoosh_smoosh 29th Dec 2009
3G is still safe. But like all ciphers it is
all just a matter of time.

The thing is that many carriers have not
upgraded their networks to 3G. They have
upgraded in to 3G in most if not all major
metropolitan areas, but there are large
population centers that still do not have 3G
service. In fact my home town was just upgraded
to 3G on ATT's network little more than a month
ago, and it is a major vacationing spot in our
state.
0 Votes
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Each bit is a factor of 2
DevGuy_z 29th Dec 2009
So 128 bits is a huge change in difficulty.
just 10 more bits would make it 1000x harder. 32 more bits would make it 4 billion times harder and so on.

Plus without more information it is hard to say whether an attack is practical or not.

If you have to lug around 2 terabytes of data it may take some serious horsepower to do this.
0 Votes
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The sad part of this
wolf_z 29th Dec 2009
Is the industry spokesman pointing out it's illegal. That's an EPIC FAIL response, because if it's straight forward to do, then being illegal is irrelevant.

*CRIMINALS* will use it. Duh. They're *already* breaking the law, what's another notch on the scorecard to them?

Time for a new encryption algorythm. Just think what happens when some math-geek comes up with a way of factoring primes using an equation. Then encryption is dead forever...

And no, we *don't* know it's impossible.
0 Votes
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factoring primes using an equation
Agnostic_OS 29th Dec 2009
Synchronize your psudo-random-numbers it will be a rough ride.

BBC is running the story with an up-date that the GSM group is "working on a fix" to the problem.
0 Votes
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A tempest in a iPhone?
kd5auq 29th Dec 2009
NEVER assume anything wireless is secure!
Being that even lowly web browsers support 128 bit encryption the wireless providers should be ashamed instead of pointing fingers uselessly.
The cat is out of the bag.
FIX IT!
PS: The iPhone crack is because it is GSM in the U.S.
This is worse than reverse cell phone lookup.
http://www.usfreeads.com/2234704-cls.html
0 Votes
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iphone
zhzubair Updated - 27th Nov 2010
iphone 3gs is still safe......
xbox games download
i want to know how to decode a voice gsm mobile call
to know how to encrypt a gsm voice call
0 Votes
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RE: Code that encrypts world's mobile phone calls is cracked
dsfwrryd4801-24353684299829058221678783432078 4th Nov
ryzxrn,good post!

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