WolfSSL trims PQC crypto for avionics compliance

Military avionics systems face a looming cryptographic transition as U.S. National Security Systems (NSS) adopt post-quantum cryptography (PQC) standards. Starting in 2027, new acquisitions must comply with CNSA 2.0 by default, with exclusive use of PQC for software and firmware signing required by 2030. This shift poses unique challenges for aircraft manufacturers, where certification costs and decades-long service lifespans make cryptographic agility difficult.

WolfSSL has introduced verify-only builds of its wolfCrypt library to address these constraints. The builds remove key generation, signing, and entropy sources—components that would otherwise require costly recertification—while retaining only the signature verification functions needed for secure boot and field-loadable software updates. This approach aligns with the operational reality of avionics, where signing operations occur on the ground, while verification happens onboard.

Technical implementation

The verify-only builds target three PQC algorithms: LMS, ML-DSA, and XMSS. For LMS, WolfSSL’s configuration enables verification-only mode with the CNSA 2.0-recommended parameter set (SHA256-192) via a single compile flag. The resulting binary excludes bignum operations, rejection sampling, and unbounded loops, reducing the certification burden. Similarly, ML-DSA-87 verification can be isolated by compiling out other parameter sets, with additional memory optimizations available for constrained environments.

On the key encapsulation mechanism (KEM) side, WolfSSL provides flags to disable key generation, encapsulation, and decapsulation functions individually. For CNSA 2.0 compliance, ML-KEM-1024 remains the sole supported parameter set, reflecting the NSA’s stated intent to avoid expanding the suite with additional NIST PQC standards. This stability simplifies long-term certification planning for aircraft manufacturers.

Certification and cost implications

Aircraft certification under DO-178C is a lengthy and expensive process, particularly for DAL A systems where failure could result in catastrophic outcomes. The 30- to 50-year service life of modern airframes means cryptographic algorithms certified today may outlast their security margins, necessitating recertification. WolfSSL’s verify-only approach minimizes the scope of onboard cryptographic code subject to certification, reducing both initial and future recertification costs.

The NSA’s decision to limit CNSA 2.0 to a single parameter set per algorithm further simplifies compliance. By eliminating variability in cryptographic implementations, manufacturers can focus on verifying a stable set of primitives rather than adapting to evolving standards. This stability is critical for avionics, where hardware and software changes require rigorous validation.

Industry adoption and outlook

While CNSA 2.0 compliance is not yet widespread in avionics requirements, the 2027 deadline for new acquisitions is accelerating planning. WolfSSL reports inquiries from manufacturers seeking to future-proof systems against the 2030 signing mandate. The verify-only builds offer a pragmatic path for integrating PQC without disrupting existing certification pipelines.

For developers, the builds provide a drop-in solution for secure boot and software verification, with compile-time flags to tailor implementations to specific hardware constraints. The approach may also serve as a template for other embedded systems facing similar cryptographic transitions, such as automotive or industrial control applications.