Quantum-Safe Networks for 6G: An Integrated Survey on PQC, QKD, and Satellite QKD with Future Perspectives

Quantum computing poses significant challenges to the current cryptographic landscape, particularly with the upcoming deployment of 6G networks. Traditional cryptographic algorithms, such as Rivest-Shamir-Adleman (RSA) and Elliptic Curve Cryptography (ECC), are vulnerable to quantum-based attacks. This vulnerability has led to the development of Post-Quantum Cryptography (PQC), Quantum Key Distribution (QKD), and Satellite-based QKD solutions. This paper provides a comprehensive review of these quantum-safe technologies, discussing their integration within the context of 6G networks. Key performance indicators (KPIs), scalability issues, and hybrid cryptographic solutions are analyzed, along with the potential of Satellite-based QKD in securing global communications. The paper also explores use cases in healthcare, financial services, defense, and autonomous systems, evaluating future research directions and issues in scaling these quantum-safe technologies across industries.