[ISN] Cell-Phone Security Far From Airtight
T Bruce Tober
octobersdad at reporters.net
Tue, 14 Apr 1998 23:58:59 +0100
fyi
------- Forwarded message follows -------
-----Original Message-----
From: jericho@dimensional.com <jericho@dimensional.com>
To: InfoSec News <isn@sekurity.org>
Date: 14 April 1998 08:23
Subject: [ISN] Cell-Phone Security Far From Airtight
>
>
>Forwarded From: Aleph One <aleph1@dfw.net>
>
>[Aleph1: Here is the real story behind the hack. BTW, you can download
> the secret GSM algorithm, COMP128, from
> http://www.scard.org/gsm/a3a8.txt]
>
> http://www.wired.com/news/news/technology/story/11630.html
>
> Cell-Phone Security Far From Airtight
> by Annaliza Savage
>
> 9:59am 13.Apr.98.PDT
> A group of California-based computer experts claims to have
> compromised the cryptographic security behind the world's most popular
> digital cell-phone system, making it possible to clone any phone using
> the GSM standard.
>
> The Smartcard Developer Association says it cracked the algorithm
> used as the basis for the The Global System for Mobile Communications
> (GSM) -- a digital cellular phone system that is used in about 80
> million cell phones, primarily in Europe and Asia. Many US networks
> are starting to implement GSM standards, too, and this attack was
> launched against a card issued by Pacific Bell. If the group's
> claims are true, it could lead to a recall or reissue of the smart
> cards used in GSM-based phones.
>
> "GSM is likely to face fraud problems of the same magnitude as analog
> systems have had," said Marc Briceno, a member of the SDA who said
> that analog systems have lost billions of dollars because of cellular
> phone cloning.
>
> GSM-based cell phones work with a small card containing an electronic
> chip called a Subscriber Identity Module card. The SIM card
> inserts into the back of the cellular phone and contains information
> that is used to identify subscribers and their account information to
> the GSM network. The SIM card must be inserted into a GSM Mobile
> handset to obtain access to the network, and one of the primary
> benefits of the technology is that cell phones have access to GSM
> networks worldwide.
>
> However, to clone a SIM card, a would-be cracker would have to have
> physical possession of one. Unlike the cloning used in analog systems,
> the crack does not yet include being able to listen in on peoples
> phone calls or obtain a SIM ID via the airwaves, although the SDA has
> stated that an "over-the-air attack should not be ruled out."
>
> The SIM uses encryption to keep the identity of the phone secret, and
> the encryption algorithm used on most of the GSM network is called
> COMP128. The SDA was able to obtain the secret ciphers used by the GSM
> network. After verifying authenticity, the group turned them over to
> UC Berkeley researchers David Wagner and Ian Goldberg, who were able
> to crack the COMP128 algorithm within a day. In 1995, Wagner and
> Goldberg succeeded in another high-profile hack when they compromised
> the crypto code used in Netscape's Navigator browser, which was
> supposed to secure credit-card transactions.
>
> "Within hours they discovered a fatal flaw," said Briceno. "The attack
> that we have done is based on sending a large number of challenges to
> the authorization module in the phone. The key can be deduced and
> recovered in about 10 hours."
>
> A group of hackers gathered with security and crypto experts Friday
> evening at a San Francisco hacker club called New Hack City, for a
> demonstration of the hack, but it never came off. Eric Hughes, a
> member of the SDA and founder of the Cypherpunks cryptography group,
> discussed the technical aspects of the hack, but had to give up the
> planned demonstration after threats of legal action from Pac Bell and
> other telephone company executives. It is illegal in the United States
> to possess cellular phone cloning equipment, although legitimate
> businesses are exempted. The telephone companies dispute SDA's claims
> to legitimacy.
>
> Wagner blames the ease of the crack on the secrecy with which the
> ciphers were kept.
>
> "There is no way that we would have been able to break the
> cryptography so quickly if the design had been subjected to public
> scrutiny," said Wagner.
>
> The GSM standard was developed and designed by the European
> Telecommunications Standard Institute, an organization that has about
> 500 members from 33 countries, representing administrations, network
> operators, manufacturers, service providers, and users.
>
> "There's going to be an orgy of finger pointing," said Hughes,
> referring to all the engineers and other people associated with the
> design of the GSM network.
>
> The SDA say that they were able to crack the GSM network algorithm due
> to weak encryption in the original design. When the system was being
> designed, several European government agencies were successful in
> their demands to weaken encryption standards for government
> surveillance purposes.
>
> The SDA also claimed that the GSM security cipher that keeps
> eavesdroppers from listening to a conversation called A5 was also made
> deliberately weaker. The A5 cipher uses a 64-bit key, but only 54 of
> the bits are actually in use -- 10 of the bits have been replaced with
> zeroes. The SDA's Briceno blames government interference.
>
> "The only party who has an interest in weakening voice privacy is the
> National Security Agency," he said.
>
> The SDA said that a proper demo will be taking place soon from
> somewhere outside the United States. The group has also released the
> source code for COMP128 and A5 for further testing.
>
>
>
>-o-
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>
tbt -- Sign all messages with non-escrowed keys, don't give in to government
tyranny. Commentary at http://www.homeusers.prestel.co.uk/crecon/Escrow.htm
--
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