The present document studies some Zero Trust Security principles that can be applied to the 5G System core network. The present document will further analyse potential threats, study necessary security enhancements, and document various decisions related to solutions as to be adopted or not adopted after evaluating the associated risks and the complexity. The present document specifically covers the following aspects:

• Analyse the 3GPP 5GS security scenarios related to the 5G core network that may benefit from a Zero Trust principle and identify the associated threats.
• Analyse the suitable Zero Trust security mechanisms (i.e. for enabling trust evaluation and ensuring trust) to address the threats identified where potential security risk exists.
• Provide recommendations for support of additional Zero Trust principles in 5GS security architecture with suitable future normative work directions, where such recommendations may include 3GPP 5G security requirements, technical enhancements, and procedural enhancements.