Hi,
> what is the content of the other half-burst in a typical FACCH usage scenario?
> if you can for example come up with significantly less than 2^57 possible
> contents of the missing half, it might be economical to guess.
Usually ... speech ...
OTOH at call establishement time there is no speech to send and the
channel could still be in signalling mode and may be filled with empty
LAPDm frames ... I never actually checked yet.
> Furthermore a lucky coincidence would be to have the second halfburst
> of the downlink and the first halfburst of the uplink (in the same
> time slot) being from 2 known LAPDm frames.
yeah, that's even more far fetched :)
Unless it's really filled with all empty frames and we could endup
with like 156+156 bits of known plaintext, giving us plenty of 64 bits
sequence to try.
Cheers,
Sylvain
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