The "worldwide effort" referred to is to generate a rainbow table of approx 2TB
making it possible to quickly determine the key given the cipherstream. This is
possible because of the short key length (48 bits) and probably some intentional
flaws in the algorithm (which would reduce the possible key space.)
Below is a story from the UK Register, and below that is an imperfect Babelfish
translation of the German Financial Times article to which it refers.
-Ed
http://www.theregister.co.uk/2009/08/25/gsm_cracked/
Mobile snooping for everyone in weeks
German hackers crack GSM encryption
By Bill Ray
25th August 2009 10:37 GMT
The Chaos Computer Club has told the FT that in the couple of months it will be
releasing code capable of cracking GSM with just a laptop and an antenna.
In comments made to the German edition of the Financial Times, the hacking group
claims
(
http://www.ftd.de/technik/it_telekommunikation/:GSM-Netz-nicht-sicher-Handys-bald-f%FCr-jedermann-abh%F6rbar/557540.html)
that governments, and criminals, are already using the technique which can break
the encryption used to protect 2G GSM calls in near-real time using existing
systems. The group says a public exposure of the technique will take place in
the next month or two and allow anyone equipped with a laptop and an antenna to
listen in to GSM phone calls.
GSM uses a range of algorithms for key generation, authentication, and
encrypting connections. This latest crack is focused on the last element which
relies on a range of algorithms known as A5 and numbered from zero to three.
A5/0 indicates that no encryption is used, such as in countries still under
ITAR* restrictions, A5/1 is the European standard that seems to be the target of
this latest breach, A5/2 is used in the USA and generally considered weaker than
A5/1, while A5/3 is the strongest of the lot and mandated by the 3G GSM standard.
GSM has been cracked before, the early algorithms used were weak and kept secret
(and thus not exposed to public scrutiny), a situation made worse by network
operators padding the keys with zeros to reduce the cost of SIM cards. This made
a weak algorithm that relied on obscurity even weaker. But since then, the
standard has proved surprisingly secure, and even today specialist equipment
will take half an hour to break a call, so real-time listening to GSM calls has
been restricted to James-Bond types with unlimited budgets.
But the Chaos Computer Club reckons they've found a way to share those super-spy
eavesdropping capabilities with anyone, which should have implications for
celebrities using mobile phones, but will probably have a more immediate impact
on low-level drug dealers who've long relied on the security of GSM for their
business.
All encryption breaks eventually, as computing power rises, and systems like GSM
are designed with a specific lifetime during which the encryption is expected to
remain secure. Changing the encryption is possible, but A5 is managed by the
handset rather than the SIM and network operators have to support legacy
handsets for long periods even if the latest models could be equipped with
better encryption.
Smartphones can, of course, opt to apply their own encryption layer on top of
the GSM, which also prevents interception at the network operator. Companies
such as CellCrypt provide Symbian and Windows Mobile clients that negotiate
their own encrypted channel without reliance on the GSM or similar.
But the rest us will probably just hold tight until everyone is using 3G
networks, at least in developed countries, where A5/3 is used and should remain
secure for another decade or two. ®
* International Traffic in Arms Regulations - US restrictions on the export of
cryptographic technology.
http://www.ftd.de/technik/it_telekommunikation/:GSM-Netz-nicht-sicher-Handys-bald-f%FCr-jedermann-abh%F6rbar/557540.html
GSM net not surely
Mobile phone soon for everyone hearable
of Maija Palmer (London)
In the next six months a wave of wire-tappings on Handytelefonate could
be approaching. Hackers work strengthened to crack the Sicherheitscode
for the GSM Handynetz. The code is to be published thereafter in the
Internet for everyone.
The portable radio standard GSM is used world-wide by approximately
three billion humans. In the case of a publication the code would arrive
inevitably into the hands of criminal ones, spies and other persons,
which have an interest to hear private telephone calls. The largest
danger would exist thereby for politicians, prominent ones and businessmen.
The chaos computer club (CCC), helps with the coordination of the
world-wide efforts to crack the GSM code. The association says, the
method, to latch itself into GSM discussions by governments and in the
organized crime is already used. One wants to make only the public
attentive on the problem. Alleged is safe the technology, but is not
correct, and humans rely around bank and other business to complete,
said the hacker Karsten Nohl. So far telephone calls could be heard only
with a highly developed equipment.
Possible, also a coded Handygespräch is to be heard, but with
commercial equipment that would take at least 30 minutes, and so for a
long time most telephone calls last not at all, said Stuart Quick of
the safety specialist Henderson Risk. Only national places create it in
few seconds.
With the cracked GSM code each hobby hacker with a 500-Euro-Laptop and a
little a Funkausrüstung could hear calls. CCC speaker Andy Mueller
Maguhn said: There are proofs for the fact that criminal organizations
and governments already use this technology, without the public of it
knows. We make the protection of the people, so that they know, what are
safe and which not.
Already one speaks in scientific reports for ten years about it, but it
is no longer theoretical only now, said Simon Bransfield Garth, boss of
the coding enterprise Cellcrypt. It could be in the next six to twelve
months a very material threat.
The commercial arm of the portable radio industry, GSMA, dismissed the
threat. It is a practical attack to be far from it. GSMA assumes the
activities of the hackers seem partly motivated by commercial
considerations. However it said to security experts that the portable
radio enterprises already know problem. You are absolutely aware of
its, but until the public does not say that they are to do somewhat
against it, them for nothing will make, around the problem to repair,
said Stuart Quick. New technologies such as 3G use a safer coding
technology and would not be not affected by the cracked code.
Received on Sat Mar 02 2024 - 00:57:18 CST