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I'm setting up test machine for my engineer work, to check GSM security and SMS interception.

I already have an N210 and read a lot of documentation. There are some questions I have but can't find on internet:

  1. Kraken works only on ATI (or AMD, don't remember which one) and need to use old PC - true or false?

  2. If I receive one malfunctioned bit from the message - I can't crack it with Kraken and rainbow tables

  3. If I crack one SMS dedicated for one person, can I use the same hash to decypher the message and don't need to search in rainbow tables again?

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Kraken works by either leveraging the CPU or an ATI video card (use `make noati' when compiling). Either one should be sufficient -- I would not recommend using an old computer or outdated hardware.

Josh Wright wrote about Kraken along with pytacle in "Hacking Exposed Wireless, 3rd Edition". He mentioned that recent GNU C Compilers do not compile the original Kraken source release, so he updated and made available a newer version of Kraken here -- https://github.com/joswr1ght/kraken

The Kraken tables from the original project must still be downloaded and utilized.

Best way to defend against this attack is to use a BYOT SIM card from a provider such as StraightTalk.

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  1. Yes, Kraken works only on old ATI cards (ATI HD4/5xxx and some 6xxx). There is a CPU version that is much slower than the GPU acceleration.

I have rewritten the cracker to OpenCL, so it runs on modern cards and even on nVidia ones. See https://brmlab.cz/project/gsm/deka/start

  1. With a few errors, it should still work, but the success rate would be much lower. Kraken works by splitting the frame to 4 114bit bursts and then each burst to 51 64bit samples and then searches for every sample. If one sample is broken, nothing disastrous happens. See the documentation of the Deka project linked above, I hope I have clearly documented how the cracker works. And feel free to ask if something is not clear.

  2. The rekeying interval depends on your phone operator. It can range from minutes to days. Until the rekeying happens, you can use the key to decrypt everything from that phone. When the rekeying happens, you have to start over.

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