The 5G protocol lacks a robust base station authentication mechanism during the initial bootstrapping phase, leaving it susceptible to threats such as fake base station attacks. Conventional solutions, including digital signatures based on Public Key Infrastructures (PKIs) and identity-based signatures, are inadequate against quantum-capable adversaries. While integrating NIST's Post-Quantum Cryptography (PQC) standards is a leading approach for quantum resistance, their suitability for 5G base station authentication remains unexplored. Moreover, current solutions are predominantly centralized and lack security features such as distributed authentication. This work presents, to our knowledge, the first comprehensive network-level performance characterization of integrating NIST-PQC standards and conventional digital signatures (including threshold and identity-based schemes) into 5G base station authentication. Our findings reveal significant feasibility concerns, with direct PQC adoption hindered by protocol constraints and large signature sizes. We also highlight the performance limitations of conventional methods due to the overhead of certificate chains. To mitigate these challenges, we propose BORG, a transitional authentication solution based on a Hierarchical Identity-Based Threshold Signature scheme with a Fail-Stop property. BORG offers post-mortem post-quantum forgery detection and distributed trust via threshold and compact signatures, well-suited for 5G's stringent requirements. Our performance analysis underscores an important warning on the infeasibility of direct PQC integration and positions BORG as an effective transitional solution toward future quantum-resilient 5G authentication.

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