CCCamp 2007: GSM A5 cracking

Steve Schear and David Hulton gave a presentation on A5 cracking. A5 is the encryption employed on GSM cellphone networks between the handset and the tower (nowhere else in the network). To sniff the GSM band, they use the GNU radio USRP. GNU radio is a software defined radio project, which given some effort you should be able to both receive and transmit in any RF band. You could use it to broadcast digital television, track radio tags, or even mess with garage door openers. For their initial investigation they used a Nokia 3310 in trace mode to dump the initial frames. Using a box with at least 27 FPGA’s they plan on constructing a 6+ terabyte rainbow table (it’ll take a couple months). Once complete, any GSM conversation can be cracked in less than 5 minutes using a single FPGA. The Hackers Choice has more info on the USRP based GSM analyzer and what they did to crack A5.


  1. confuted says:

    The gnu radio/usrp project looks really neat. It claims to reduce radio problems to software problems, but it actually looks to reduce radio problems to the problem of buying a $700 usrp, and a software problem. If the radio was cheaper (sub $150), that would be a lot of fun to play with, but $700 is too much.

  2. Jay says:

    Does this work with the other ancient cell phone system. CDMA, PCS etc? This was my main concern when choosing a cell phone provider. I heard that there was a way to mess with gsm so I went with cdma.

  3. RusH says:

    weird, I read a paper that said you can pretty much crack A5 in real time on P133MHz laptop, it was circa 1995

  4. RusH says:
    After a 2^48 parallelizable data preparation stage (which has to be carried out only once), the actual attacks can be carried out in real time on a single PC

    280GB rainbow tables, but realtime after that

  5. srilyk says:

    So when you get your openmako, you one up them and hack the hack. Sweet ;)

  6. VUGO says:

    Well, i am interested in some hardware/stuff to intercept GSM calls in pseudo/real-time. I can pay USD3.000,00 to this. If anybody can do this, please contact me in h2glabs “AT” or vugo “at” I am brazilian, so, sorry to my bad english. Regards.

  7. nathan belomy says:

    the aliens built it!

  8. LordB says:

    rush, that is an old attack. Read about the best currently known attack here:

  9. tristan says:

    how can i hack a gsm network to run and use a motorola Q cdma phone?

  10. viper says:

    why i can’t acses ?
    can u help me….
    maybe u have another link or share it @rapid/ziddu
    thx alot

  11. kurye says:

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  12. kurye says:

    emege saygi tesekkürler devamini bekleriz.

  13. kurye says:

    Eline sağlık güzel olmuş devamını bekleriz!!

  14. Kurye says:

    İstanbul içi moto kurye servisleri için;
    0212 217 36 36 PBX

  15. So when you get your openmako, you one up them and hack the hack. Sweet ;)

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