AKMA+: Security and Privacy-Enhanced and Standard-Compatible AKMA for 5G Communication

The Authentication and Key Management for Applications (AKMA) protocol is a fundamental building block for security and privacy of 5G cellular networks. Therefore, it is critical that the protocol is free of vulnerabilities that can be exploited by attackers. Unfortunately, based on a detailed analysis of AKMA, we show that AKMA has several vulnerabilities that may lead to security and privacy breaches.

We define AKMA+, an enhanced protocol for 5G communication that protects against security and privacy breaches while maintaining compatibility with existing standards. AKMA+ includes countermeasures for protecting communication between the user equipment (UE) and application functions (AFs) from attackers, including those within the home public land mobile network. These countermeasures ensure mutual authentication between the UE and the AKMA anchor function without altering the protocol flow. We also address vulnerabilities related to subscriber and AKMA key identifiers that could be exploited in linkability attacks. By obfuscating this data, AKMA+ prevents attackers from associating a target UE with its past application access.

We employ formal verification to demonstrate that AKMA+ achieves key security and privacy objectives. We conduct extensive experiments demonstrating that AKMA+ incurs acceptable computational overhead, bandwidth costs, and UE battery consumption.