Designing for FIPS 140-3: A Practical Guide for Engineering

Beyond security, adherence to FIPS 140-3 can support interoperability, repeatable deployments, and predictable audit outcomes across complex systems.

FIPS 140‑3 defines standardized security requirements for cryptographic modules across:

• Algorithm selection and cryptographic primitives
• Key generation, handling, and destruction
• Entropy sources and DRBG validation
• Physical security protections (for hardware)
• Secure boot, self‑tests, integrity checks, and error handling
• Boundary definitions and operational environments

Getting these engineering decisions right at design time minimizes the risk of costly rework, failed validations, and security gaps. Treating FIPS 140‑3 as a design discipline — not a post‑development audit, is critical.

FIPS 140‑3 requirements shape both architecture and implementation. Engineers must consider how security functions behave from the moment the system boots through runtime operations and updates.

Examples of core engineering decisions influenced by FIPS requirements include:

• Choosing cryptographic libraries: Whether to use an open‑source module (e.g., OpenSSL FIPS provider), create a proprietary one, or privately label a validated module.
• Boundary scoping: Deciding whether the “cryptographic boundary” is your entire product, a subcomponent, or a standalone module.
• Entropy design: Ensuring your RNG/DRBG meets SP 800‑90 requirements and that entropy collection is testable and well‑documented.
• Integrity monitoring: Implementing pre‑operational self‑tests and approved integrity checks that must pass before the module enters a FIPS‑approved mode.

Evaluating these design decisions early helps prevent failures during testing.

Bridging security design with practical engineering execution is where many FIPS efforts succeed — or fail. This is the point in the development lifecycle where theoretical security requirements become engineering realities. Attempting to “retrofit” FIPS into an existing product is a common engineering failure. Corsec recommends integrating FIPS security requirements from the initial architectural design to reduce rework, cost, and validation delays. As an example, a team that chooses a non‑approved AES mode of operation (such as AES‑XTS for certain contexts) will later be forced to redesign its crypto pipeline once CMVP testing begins.

Plan for Compliance from Day One
Designing with FIPS 140-3 requirements in mind from the start—rather than attempting to retrofit compliance late in development—reduces engineering rework, lowers costs, and shortens validation timelines.

Document Gaps Using a POA&M
The most essential mitigation strategy is documenting certification gaps. For engineers, this means clearly identifying and outlining validation boundary options and the technical areas that need to be addressed in order to achieve validation.

Enforce FIPS-Approved Mode Configuration
Validated modules must operate strictly in their FIPS-approved mode. Misconfiguration is a common engineering pitfall and one of the most frequent causes of non-compliance during reviews.

Use Approved Security Update Paths
When addressing CVEs or updating to a newer version of your product, engineers should select and follow the appropriate and approved security update process. There are many different update scenarios available for modules, some paths are faster and more cost-effective than triggering a full revalidation. Keeping your module inline with the regulations to qualify for an update is key.

Select an Appropriate FIPS Partner
Involving a FIPS partner early in the development lifecycle allows engineers to receive feedback before designs are finalized. Early engagement helps ensure documentation accuracy and reduces the likelihood of delays during formal testing.

Reviewing FIPS requirements at every engineering milestone is highly recommended, from architecture to final testing.

Ready to Engineer Your Product for FIPS 140‑3?

If you’re building cryptographic products for federal or regulated markets, Corsec recommends engaging early to avoid costly engineering rework.

To accelerate your path to validation and ensure your engineering team is building FIPS‑ready designs from day one, schedule time to speak to a Corsec engineer.