a5/1 uplink cracking

[Peter Wallereres]

anyone tried to modify the find_kc for uplink cracking, i tried but died not succeed, maybe anyone can help me please?

[Nikos Balkanas]

Hi Peter,

gr_gsm doesn't crack keys. kraken does.

Where did you find that function? In kraken?

It's not from gr_gsm. Have you tried the kraken list?

BR

Nikos

On Fri, Mar 28, 2025 at 5:36 PM Peter Wallereres <peter.wa...@gmail.com> wrote:

anyone tried to modify the find_kc for uplink cracking, i tried but died not succeed, maybe anyone can help me please?

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[Nikos Balkanas]

Hi Peter,

Please address list, so that others may benefit or offer help.

gr-gsm doesn't have a client loop. That means that uplink bursts are treated as downlink

ones. Piotr in his example cfile has treated both downlink and uplink traffic, but needed

external clock synchronization for that.

I have not tried this myself, but immediate assignment extracts frame number from the headers.

gr-gsm/lib/misc_utils/extract_immediate_assignment_impl.cc

That part is right. My guess is that frame number is maintained for other bursts. That means

that if you mix in uplink bursts, it will be off:(

HTH

Nikos

On Sat, Mar 29, 2025 at 7:18 PM Peter Wallereres <peter.wa...@gmail.com> wrote:

Hello Nikos, thank you for the

reply, Sorry to post it here, of cause you are right,

it is a kraken tool, I will ask in the a51 list about it,

but i doubt to get an answer, as the latest post there is from 2/2013!

But maybe you can tell me, if the framenumbers and the framecounts

of uplink bursts in gr-gsm bursts printer blocks are real ones. It tried to use them

in the modifing find_kc with the need 114 back clocking steps but matched

kc for know several ul-plaintxt bursts is not found. the kc is known, but no

success, so i wonder what i am doing wrong...

[Piotr Krysik]

Hello,

There is a bit in ARFCN field of GSMTAP header that signals if it is
downlink or uplink burst. It is being set by the receiver. So it's
possible to distinguish uplink from downlink bursts based on that.

There is also (but not ported yet in the porting_to_3.11 branch)
uplink/downlink splitter that lets you i.e. to decode uplink and
downlink bursts sparately. Because the uplink and downlink messages
won't be synchronized because they will be sent using asynchronous
message passing from different decoding blocks. If you need to have them
synchronized then you will have to implement missing functionality -
either by extending the decoder so it can decode uplink and downlink
separately or add some block that will resynchronize uplink and downlink
messages (this might be more challenging to do right).

Best Regards,
Piotr Krysik

W dniu 29.03.2025 o 21:11, Nikos Balkanas pisze:

> <nbal...@gmail.com <mailto:nbal...@gmail.com>>:

>
> Hi Peter,
>
> gr_gsm doesn't crack keys. kraken does.
> Where did you find that function? In kraken?
> It's not from gr_gsm. Have you tried the kraken list?
>
> BR
> Nikos
>
> On Fri, Mar 28, 2025 at 5:36 PM Peter Wallereres

> <peter.wa...@gmail.com <mailto:peter.wa...@gmail.com>>

> wrote:
>
> anyone tried to modify the find_kc for uplink cracking, i
> tried but died not succeed, maybe anyone can help me please?
>
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> msgid/gr-gsm/772b73f2-208d-49e2-

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Piotr Krysik