Security Coverage: Assuring Comprehensive Security in Hardware Design

As hardware systems become increasingly complex and security threats grow more sophisticated, ensuring robust hardware security during the pre-silicon phase of development is more critical than ever. Cycuity’s white paper outlines how its Radix platform enables engineers to verify, visualize, and measure the effectiveness of hardware security throughout the design lifecycle, ultimately ensuring compliance, minimizing vulnerabilities, and building trust with customers, auditors, and regulators.

Radix provides security coverage through a data-driven approach that quantifies how thoroughly security verification has been applied to a hardware design. Like functional coverage in traditional verification, security coverage ensures that protection mechanisms and policies are not only in place but are rigorously exercised and validated during simulation or emulation. This enables design teams to identify and address vulnerabilities early, avoiding expensive post-silicon fixes and reducing overall risk.

The verification of hardware security features is split into two main activities: functional security verification and security protection verification. Functional security verification ensures that security components behave as expected. For example, a test might check whether a cryptographic key reaches the AES encryption block within a specified time frame when requested. This aspect of verification is often addressed using traditional techniques like formal verification, assertions, and directed tests.

In contrast, security protection verification addresses broader questions, such as whether sensitive data might inadvertently escape a chip’s boundary. This approach verifies that protections are in place to prevent unintended or unauthorized data flows, and it enables a more system-level perspective. While functional verification focuses on specific, localized behaviors, protection verification considers the full design over extended time periods and wider spatial contexts.

Cycuity’s Radix technology supports both types of verification and introduces security coverage metrics to evaluate the thoroughness of these efforts. These metrics show how well security requirements—like ensuring a key never exits a secure module—have been tested under various conditions. The platform allows security teams to define assets, specify security rules, and track whether these rules are upheld in practice. When rules are violated or not sufficiently exercised, Radix offers powerful debug tools including waveform, RTL, and schematic views that pinpoint information flow issues.

The concept of a protection boundary is central to Radix’s methodology. This refers to circuit logic that confines secure data within specific areas, preventing leakage or misuse. For instance, a control signal might be required to gate the release of encrypted data, thereby establishing a hardware-based boundary. Security coverage tracks whether this boundary has been properly implemented and whether all relevant paths leading to and from it have been adequately tested.

To calculate security coverage, Radix monitors information flow between a source (like a secure key) and its destination (such as a system output). Toggle coverage—a standard verification metric used to track how often signals change—is collected across test runs and merged into a comprehensive database. Radix then analyzes this database to produce a security coverage metric, which is visualized through its user interface. This GUI highlights problem areas and enables cross-probing into schematics and RTL code for further analysis.

Low security coverage may result from several factors, including misconfigured protection boundaries, insufficient test coverage, or flawed RTL implementations. Radix helps identify the root cause and allows teams to adjust designs or add targeted tests. This iterative process is akin to achieving functional coverage and is essential for preparing a design for final security signoff.

The value of security coverage extends beyond internal development. The reports generated by Radix offer credible, visual, and actionable evidence of compliance with standards like ISO 21434 and the NIST cybersecurity framework. These reports are useful for customers, regulators, and auditors seeking transparency and assurance.

In conclusion, Cycuity’s Radix platform brings much-needed rigor and visibility to pre-silicon hardware security. By defining, measuring, and analyzing security coverage, Radix empowers engineering teams to deliver secure silicon with confidence. It bridges the gap between design intent and implementation reality, helping organizations not only meet compliance requirements but also enhance trust, accountability, and resilience in their hardware products.

You can download this whitepaper here.

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