[srslte-users] RRC Security Mode Command Failure

[Pedro Alvarez]

Hi David,

Thanks for reporting, I'll look into this.
You're probably right, it's probably  a mis-match between the UE's and
the EPC's UL NAS COUNT.

Could you try to do the following, just so I can be sure the problem
is what I think it is:

  1 - Force an IMSI attach. You should be able to do this by taking
out the SIM and putting it in again, or by putting the . (This should
work fine.)
  2 - Do a GUTI attach without restarting the EPC. You can do this by
going in and out of  flight mode. (This should still work fine.)
  3 - Re-start the eNB and the EPC and try the GUTI attach again.
(This is probably where it's failing.)

Regards,
Pedro

On Wed, Apr 4, 2018 at 1:45 PM, David Rupprecht <david.rupprecht at rub.de> wrote:
> Hi,
>
> I'm using srsepc and srsenb in the latest version (1803). When trying to
> connect a commercial UE with a programmable SIM card to the enB and EPC,
> I get a RRC Security Mode Failure from the UE. My first guess, was that
> the key_enb was not correctly transmitted, but this is not the case.
> Maybe the k_enb is not correctly derived (NAS_UL_COUNT?), but I have not
> checked that. Do you have any suggestions?
>
> With an older version of the srsEPC and the latest eNodeB the attach
> works without any problems.
>
> I have attached the logs.
>
>
> Best regards,
> David
> --
> M.Sc. David Rupprecht
>
> Ruhr-University Bochum
> Research Group Information Security
> Universitätsstraße 150
> ID 2/130
> 44780 Bochum / Germany
>
> Phone: +49 234 / 32 - 23508
> Web: www.infsec.rub.de
>
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