Mobile network operators face a complex and urgent challenge in preparing for post-quantum cryptography (PQC), according to Dr. Yaakov Stein, VP CTO of Allot. While some traffic, like subscriber voice calls or web browsing, quickly loses sensitivity, critical data such as subscriber identity mappings, billing records, and call metadata can remain sensitive for years, necessitating PQC protection. Financial transactions, including credit card information, also require long-term protection, though this is often handled by subscriber-side applications.
The initial step for any operator is to conduct a thorough inventory of all public-key cryptography usage. This includes identifying 5G Service-Based Architecture (SBA) interfaces, Internet Key Exchange (IKE) for IPsec-protected links, DNSSEC, and encrypted APIs. A comprehensive inventory is crucial to avoid later oversights.
Following the inventory, the next priority is to migrate all TLS-dependent systems, including SBA interfaces, Security Edge Protection Proxy (SEPP), web portals, and Operations Support System/Business Support System (OSS/BSS) APIs, to hybrid key exchange. This technology is currently the most readily available for PQC migration. Subsequently, IPsec links, encompassing backhaul, inter-data center connections, and LTE roaming interfaces, should undergo a similar migration. Other public-key reliant protocols, including proprietary ones, should then be addressed.
Once key exchanges are secured, operators can focus on authenticating long-lived connections, which can accommodate the larger public keys associated with current PQC digital signatures. Software authentication for short-lived connections can be deferred, as can hardware authentication and attestation mechanisms, which depend on vendor readiness. While 5G subscriber authentication largely relies on symmetric keys, the underlying Public Key Infrastructure (PKI) still requires PQC consideration.
For operators limited to a single PQC deployment in a given year, the most impactful measure is to deploy hybrid ML-KEM (specifically, X25519 ECC with ML-KEM, ideally with crypto-agile backup to HQC) on all TLS-protected SBA and management-plane interfaces. This represents the most accessible and effective initial step.
Operators should be wary of vendor responses that indicate a lack of understanding or a delay tactic regarding PQC. Statements such as "we are waiting for the standards to stabilize" are concerning, as PQC standardization is progressing rapidly, and crypto-agility is key to future-proofing. Similarly, claims that "cryptographically relevant quantum computers are still not here" or that "our encryption is based on symmetric encryption and so quantum safe" are red flags, suggesting either a misunderstanding of the threat or intentional misdirection.
The most common failure in an operator's PQC migration is not a cryptographic breach but an operational oversight. This typically stems from an incomplete crypto inventory, leading to the neglect of an interface such as an SSH-accessible machine, an old RADIUS interface, a load balancer, a NAT device, or an unmaintained orchestration tool. Such omissions create a false sense of security, as PQC readiness is only as strong as its weakest link. Additionally, new PQC mechanisms can sometimes disrupt legacy equipment, as seen with early implementations of Kyber, which caused issues with middleboxes due to multi-packet TLS client hellos and required rollback.
