Organizations Advised to Expand Threat Modeling in Preparation for Quantum-Era Attacks
Microsoft is encouraging organizations to expand threat-modeling exercises to uncover cryptographic dependencies that could leave applications and data vulnerable to future quantum computing attacks.
The transition to post-quantum cryptography, or PQC, requires more than replacing a few encryption algorithms. Organizations must first determine where cryptography is used, what information it protects, and whether the underlying technology can be upgraded without major architectural changes, Microsoft researchers Michael Howard and Simone Curzi explained in a recent blog post.
"Building a complete cryptographic inventory is difficult," the researchers wrote.
Automated scanning tools can identify many cryptographic libraries and dependencies, but Microsoft said they may overlook controls supplied by operating systems, cloud platforms, third-party frameworks, and hardware. They can also miss architectural assumptions and indirect dependencies that are visible only when teams examine how a system was designed.
Threat modeling can help close those gaps by forcing development and security teams to trace how data moves through an application, where trust boundaries exist, and which security controls protect critical assets.
"Threat modeling often captures information that is highly valuable," Microsoft said.
For PQC planning, those exercises should go deeper than documenting that data is encrypted in transit or at rest. Teams should record the algorithms, protocol versions, cipher suites, key sizes, and implementation providers used by each component.
They should also determine who owns each cryptographic dependency, how long protected data must remain confidential, and whether an outside provider controls the timetable for upgrading a service.
Microsoft offered a lengthy list of questions organizations can add to existing threat-modeling reviews. Those include whether RSA or elliptic-curve cryptography is used for key exchange or digital signatures, whether algorithms are hard-coded, and whether hardware security modules, Trusted Platform Modules or secure enclaves can support PQC.
"The questions we have listed here are far from exhaustive," the researchers cautioned.
Microsoft's guidance recommends TLS 1.3 as the required foundation for post-quantum network protection. However, simply using TLS 1.3 does not make a connection quantum-resistant. The connection must also negotiate a supported post-quantum or hybrid key-establishment group.
The company recommends organizations move from RSA, ECDH and Diffie-Hellman key establishment to ML-KEM. Microsoft also points to ML-DSA, SLH-DSA, or composite signatures as successors to RSA- and elliptic-curve-based digital signatures. For bulk encryption, Microsoft recommends AES-256.
For more information, read the Microsoft blog here.