Sign in Subscribe

5G NAS Authentication Failures Cause Values

Last updated on 

5G (fifth-generation) cellular networks introduce several changes compared to their predecessors, and one of these changes involves the authentication process. The 5G system is designed to offer enhanced security and efficiency, and one aspect of this is the handling of authentication failures.

When a device, such as a smartphone or any other 5G-capable device, attempts to connect to a 5G network, it undergoes a series of authentication procedures to ensure its legitimacy and security. The Non-Access Stratum (NAS) is a layer in the 5G architecture responsible for handling signaling procedures like registration, connection, and authentication.

1. NAS Authentication in 5G:

In 5G, the NAS authentication is performed using the Authentication and Key Agreement (AKA) mechanism, which is an enhanced version compared to 4G. During this process, various messages are exchanged between the device and the core network (specifically, the Authentication Server Function or AUSF).

2. Cause Values for NAS Authentication Failures:

In the context of 5G NAS authentication, a 'cause value' is a specific code that indicates the reason for a particular authentication failure. These cause values provide detailed information about why an authentication procedure failed, facilitating troubleshooting and diagnostic efforts.

Here are some potential cause values for NAS authentication failures in 5G:

  • EAP-AKA' challenge failed: The Extensible Authentication Protocol (EAP) method AKA' challenge-response failed during the authentication procedure.
  • MAC failure: The Message Authentication Code (MAC) verification failed, suggesting potential tampering or integrity issues with the NAS messages.
  • Sync failure: There was a synchronization failure between the device and the network during the authentication process.
  • Security mode rejected: The security mode proposed by the device was rejected by the network, possibly due to compatibility or configuration issues.
  • Non-5G access: The device attempted to use 5G authentication procedures while operating in a non-5G (legacy) access mode.

3. Implications and Troubleshooting:

Understanding these cause values is crucial for diagnosing and resolving authentication issues in 5G networks. When an authentication failure occurs, the network and device operators can refer to the cause value to identify the specific reason behind the failure. This information then guides the troubleshooting process, allowing for targeted interventions to address the underlying issue.