[srslte-users] Connecting any phone to srsENB

[Merlin Chlosta]

Hi David,

I think you’re right that all phones require credentials to access the network. Usually, these credentials are stored on USIM (phone side). On the network side, a node called HSS (Home Subscriber Server) stores the keys. In srsLTE this is just the user_db.csv, in big core networks it’s actually a server running. When you connect, the credentials are fetched from this server. Now with roaming, the "visited network" ( the one you just wirelessly connected to) searches for your "home operator’s" HSS to fetch the credentials. Both networks have some agreement that allows access to the HSS. So there are always the keys involved. To my understanding, the only way for un-authenticated access are emergency calls.

My knowledge on the USIM is really limited, but I think that any OTA communication requires authentication — thus, the keys or some certificate on the SIM. In the end, all trust in LTE is derived from the USIM. It would be a severe issue if any network could just read the secrets from customers of other networks.

Viele Grüße
Merlin

> On 6. May 2020, at 03:09, David Hitchcock <dhitchcock at POC.com> wrote:
> 
> srsLTE team,
>  
> Great software! Thanks for all the hard work!
>  
> I have setup a srsLTE network with srslte eNodeB connected to an unlocked phone with a test SIM card from sysmocom. No problem there.
>  
> Now I have, perhaps a dumb question. Is there some way to allow any phone to connect to the srsenb network? I doubt it, since the parameters stored in the phone’s USIM card must be added to the ‘user_db.csv’ file. Yet, I am a bit confused with the roaming process, where a phone can ‘roam’ on another network with the right permissions and traceability (for billing). Is there some way an off-the-shelf phone can ‘roam’ on the srsLTE eNodeB as they do on other networks?
>  
> Failing that, (which seems likely) is there some Over The Air (OTA) process that can read the required parameters, which can then be added to ‘user_db.csv’?
>  
> Thanks,
> David
> 
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