When the core network uses a non-empty encryption algorithm, the UE cannot attach correctly

[liuxiaoxinxinxin]

Hello,

I set up the environment according to the guidance from s5uishida/free5gc_srsran_sample_config, using free5gc as the core network and srsRAN Project as the base station, with srsRAN 4G as the UE.

When using NEA0 in the free5gc core network AMF configuration file, meaning the encryption algorithm is NEA0, the UE can successfully attach (NEA0 with NIA1, NIA2 or NIA3). However, when the encryption algorithm is not NULL (like NEA1 with NIA1), the UE fails to attach. The specific reason is that the UE cannot parse the initial context setup (registration accept) sent by the core network.

We found that when the UE parses the registration accept message, the inner extended protocol discriminator it decodes is incorrect.

Have you ever had the opportunity to use encryption algorithms, or do you have any suggestions or assistance you could offer?

Thank you!