Aligning on Machine-Readable Signals as the Foundation for Due Diligence

By Madalin Neag, EU Policy Advisor, OpenSSF

Introduction

The software supply chain has reached a level of complexity where manual oversight is no longer a viable strategy for security or regulatory compliance. Modern systems depend on vast, rapidly evolving networks of components, making manual, paper-based approaches to due diligence impractical. Machine-readable, continuously generated security signals are therefore the only realistic way to support Cyber Resilience Act (CRA) due diligence at scale. These signals already exist across open source ecosystems as a natural byproduct of standard development practices, though they remain fragmented across tools, repositories, and pipelines. Crucially, these signals are best understood as mechanisms for transparency rather than assurance: they expose observable characteristics of software development and operational behavior without constituting guarantees, certifications, or transfers of liability. 

This shift is driven by a need for technical accuracy. Static documentation and point-in-time attestations cannot reflect continuously evolving software systems. This limitation has been underscored by recent U.S. enforcement actions, such as Department of Justice settlements involving inaccurate cybersecurity compliance certifications, which highlight how formal attestations can later be treated as misleading when they diverge from actual system behavior, significantly increasing legal exposure.

Established approaches such as continuous compliance, evidence-based assurance, and secure-by-design all rely on the same principle: replacing subjective, point-in-time claims with dynamic, verifiable proof, automated data that reflects actual system behavior.

Within this model, roles remain clearly separated. Upstream open source projects may choose to publish security-relevant signals in machine-readable formats, while manufacturers, who bear the legal responsibility under the CRA, consume and interpret this information as part of their due diligence processes. This preserves the foundational “no warranties, no liabilities” principle of open source. Participation from upstream remains strictly voluntary and must not introduce legal obligations, certification expectations, or shifting of compliance risk and liability to the project community, ensuring that ecosystem sustainability is maintained while enabling effective downstream risk management.

This discussion builds on earlier reflections on voluntary attestation models under the Cyber Resilience Act, particularly Article 25, which enables voluntary security attestation programmes to support manufacturer due diligence for products incorporating free and open source software while preserving the separation between upstream development and downstream regulatory responsibility. From a systems perspective, however, Article 25 also exposes an important limitation of paper-based attestation approaches. Static, human-authored representations of security struggle to remain accurate within environments defined by continuous change, where rapidly evolving components and deeply nested dependencies can quickly render point-in-time attestations incomplete or outdated. This leads to a broader architectural observation: effective due diligence at scale increasingly shifts away from narrative declarations toward machine-readable, continuously updated security signals embedded directly within development and release workflows. In this framing, voluntary attestation is valuable not as a mechanism for upstream certification, but as a way to enable structured, interoperable security data that downstream systems can automatically consume and evaluate. Machine-readable signals thus become the practical substrate for operationalizing the intent of Article 25 in complex software ecosystems, preserving voluntariness, avoiding any conflation of transparency with assurance, and enabling evidence-based due diligence aligned with the dynamic nature of modern software systems.  

Due Diligence under the CRA: a continuous risk-based process

Due diligence under the CRA must be understood as a continuous, risk-based obligation rather than a procedural formality. As clarified in the European Commission’s FAQ and further complemented via the CEN PT1 standard, it is not a checklist to complete or a document to obtain, but an ongoing responsibility carried by manufacturers placing products with digital elements on the market. Its purpose is to ensure that third-party components, regardless of origin, do not compromise the cybersecurity of the final product.

At its core, due diligence requires manufacturers to make informed, traceable decisions about the software they integrate. This includes understanding the origin and role of components, evaluating their security characteristics, and determining whether their use is appropriate within the context of the product. These activities form a continuous lifecycle process covering evaluation, integration, monitoring, and remediation. The level of scrutiny applied is inherently risk-based and contextual, and depends on the role, exposure, and criticality of each component within the manufacturer’s system.

This obligation is dynamic by nature. Software components evolve, vulnerabilities are disclosed continuously, and integration contexts change over time. Due diligence therefore extends across the entire lifecycle, requiring manufacturers to revisit earlier assumptions and adjust mitigation strategies as new information becomes available. This creates a continuous feedback loop between upstream changes and downstream risk decisions.

The regulatory expectation is that this process is demonstrable through technical documentation that allows decisions and risk assessments to be traced and verified. The emphasis is not on collecting predefined assurances, but on ensuring that decision-making remains consistent, auditable, and defensible over time.

For open source components, due diligence relies on observable project characteristics rather than formal assurances. Manufacturers assess elements such as maintenance activity, responsiveness to security reports, release practices, and the availability of structured security documentation, drawing on signals that reflect how a project is actually developed and maintained. These signals can be aggregated into continuously updated, machine-readable evidence reflecting the current security posture of both the component and its dependencies. This approach does not create any dependency on upstream attestations: under the CRA, manufacturers remain solely responsible for their assessments, while any transparency provided by open source projects is entirely voluntary and does not constitute certification or liability. Machine-readable security signals therefore function primarily as decision-support inputs within downstream risk management processes. They improve the quality, consistency, and scalability of due diligence activities, but they do not replace the manufacturer’s obligation to exercise independent judgment and accountability. 

Machine-Readable Signals in Practice

A mature ecosystem of tools already generates machine-readable signals that can support due diligence under the CRA. These signals span multiple layers of the software lifecycle, from component identification to vulnerability management and build integrity. Standards such as SPDX and CycloneDX enable structured software bills of materials (SBOMs), while frameworks like SLSA define levels of build provenance and integrity. Complementary technologies such as Sigstore provide cryptographic mechanisms to verify artifacts, and formats like CSAF and VEX support the structured exchange of vulnerability and exploitability information. Tools such as SBOM CVE Check, Dependency-Track, Syft, and Grype operationalize these standards by enabling SBOM-driven component analysis and automated vulnerability scanning, while SBOMQS provides additional validation of SBOM quality and compliance against established standards.

Within the OpenSSF ecosystem, these capabilities are reinforced by a growing set of complementary tools that standardize, expose, and operationalize security-relevant signals across different layers of the software lifecycle. Some focus on repository security posture and development practices, others on supply chain integrity and provenance, while newer systems increasingly aggregate these signals into unified, queryable models suitable for large-scale risk analysis and automated due diligence workflows. At the project governance and security posture layer, OpenSSF Scorecard provides automated checks on repository hygiene and secure development practices, while the Best Practices Badge and Open Source Project Security (OSPS) Baseline initiatives offer structured indicators of project maturity and security adoption. OpenSSF Security Insights extends this approach by introducing a standardized, machine-readable format for publishing security policies, development processes, and maintenance practices, enabling more consistent interpretation of project security posture across tools and downstream consumers. Complementing these efforts, LFX Insights aggregates operational and community signals related to project activity, contributor diversity, governance, and security posture, helping organizations evaluate the long-term sustainability and operational health of dependencies over time. Together, these tools transform otherwise fragmented repository metadata into reusable signals that support risk-based evaluation without requiring additional compliance artifacts from maintainers. 

At the supply chain integrity layer, frameworks such as in-toto provide cryptographically verifiable attestations describing individual steps within software build and release pipelines, strengthening provenance visibility and artifact integrity. SBOMit builds on this model by combining SBOM generation with in-toto attestations and signed supply chain layouts, enabling verifiable component composition during the build process. Related tooling such as Protobom and Bomctl improves interoperability and operational reuse of SBOM data. Protobom provides a format-neutral intermediate representation that allows SPDX and CycloneDX documents to be transformed and consumed consistently across heterogeneous tooling ecosystems, while Bomctl enables structured manipulation, merging, and management of SBOM trees across complex dependency environments.

Increasingly, these signals are being aggregated into higher-level analytical systems capable of supporting continuous, ecosystem-scale risk analysis. GUAC (Graph for Understanding Artifact Composition) demonstrates this direction by ingesting SBOMs, provenance attestations, vulnerability reports, OpenSSF Scorecard results, and related metadata into a continuously queryable graph model. This enables dependency-aware analysis of upstream risk exposure, artifact relationships, and vulnerability propagation across software ecosystems. Architecturally, systems such as GUAC illustrate a broader shift within software supply chain security: compliance and due diligence increasingly become problems of correlating continuously generated technical evidence rather than collecting static documentation.  

Additionally, tools and frameworks such as OSS Review Toolkit (ORT), Community Health Analytics in Open Source Software (CHAOSS), and OpenChain extend this landscape by enabling deeper analysis and contextual understanding. ORT integrates dependency, license, and vulnerability analysis into reproducible workflows, while CHAOSS provides metrics on project activity, health, and sustainability. OpenChain complements these by defining standards for open source compliance and supply chain governance, helping organizations establish consistent, auditable processes for managing open source use. Together, these perspectives allow manufacturers to assess not only technical risk but also organizational maturity and long-term sustainability of the components on which they depend.

This direction is also reflected in European cybersecurity guidance. ENISA’s Security by Design and Default Playbook highlights machine-readable signals as a mechanism for making security both demonstrable and verifiable within development processes. By enabling continuously generated, machine-consumable evidence that can be automatically validated and reused, this approach reinforces the shift from static documentation to dynamic, lifecycle-integrated assurance, directly supporting scalable due diligence.

European initiatives further build on this foundation by operationalizing these signals into compliance workflows. EU-funded projects such as CRACoWi, CYBERFORT, CONFIRMATE, OSCRAT, and OCCTET ingest machine-readable inputs (including SBOMs, vulnerability data, and provenance information) and transform them into risk assessments and technical documentation. These platforms demonstrate how compliance can be implemented as a continuous, automated process, reinforcing the complementarity between upstream signal generation and downstream consumption.

Taken together, these tools form an interoperable ecosystem of continuously generated signals. They already provide most inputs required for effective due diligence, demonstrating that the necessary data exists within current development workflows. This confirms a key architectural reality: compliance at scale is fundamentally a data integration problem, not a documentation problem.

A large share of due diligence-relevant information is already present within open source repositories. Security policies (SECURITY.md, security.txt), contribution workflows (CONTRIBUTING.md), release histories (changelogs), issue templates, licensing files, and repository governance practices (branch protection, maintainer authentication) collectively describe how software is developed, maintained, and secured. Together, they provide a rich baseline for assessing development discipline, update reliability, and supply chain integrity, without requiring additional compliance artifacts.

However, these signals are often distributed across heterogeneous formats and locations, making them difficult to discover and reuse at scale. Improving their visibility through lightweight structuring or simple indexing can significantly reduce friction. This is not about adding new artifacts, but about improving the accessibility of existing ones.

The viability of this model is already demonstrated in practice. Many open source projects publish structured security information as part of their normal operations. Projects such as K3s provide comprehensive self-assessments describing architecture and security considerations, while the Argo project maintains clear documentation of its vulnerability disclosure processes. Other initiatives, including Privateer and other projects within the CNCF ecosystem, expose structured security information directly within their repositories. These projects demonstrate that “CRA readiness” is essentially an extension of existing high-quality security engineering. Documenting security posture is already a well-established practice; what is missing is not the content, but a consistent way to connect that content to automated due diligence workflows.

Guidance from OpenSSF security assessments further supports this practice by helping projects think systematically about their security posture, development processes, and risk boundaries.

This becomes particularly critical at scale. Modern systems depend on hundreds or thousands of components, making manual evaluation (and reliance on manual, individualized attestations) infeasible. Machine-readable signals enable automated collection, continuous updates, and consistent analysis across dependency graphs, transforming due diligence into a reproducible computational workflow aligned with contemporary software realities.

Voluntary Upstream Participation and Ecosystem Engagement

It is critical to start with a baseline legal protection: maintainers and stewards are not “suppliers” in a commercial sense and are not required or expected to sign contracts or guarantee compliance outcomes. Under the CRA, open source projects are under no obligation to support compliance activities. Responsibility remains exclusively with manufacturers placing products on the market. This legal boundary is intentional and reflects the regulation’s effort to preserve the open source model, particularly the “no warranties, no liabilities” foundation that enables broad participation and innovation. More broadly, the legislative intent of the CRA is to protect the “long tail” of community-driven innovation, ensuring that smaller projects, individual maintainers, and informal communities are not burdened with obligations designed for commercial actors.

At the same time, many projects already choose to publish security-relevant information such as vulnerability handling policies, release processes, or build metadata. These actions improve transparency and usability for downstream users, but they do not create legal obligations, warranties, or liability. They are best understood as voluntary engineering practices that reduce friction and make projects easier to adopt within regulated environments.

A central principle throughout this model is the clear distinction between transparency and assurance. Transparency refers to voluntarily published, descriptive information about how software is developed, maintained, and secured. Assurance, by contrast, implies some form of validated guarantee, certification, or assumption of responsibility. Under the CRA and within open source ecosystems, transparency must never be interpreted as assurance. 

Any attempt to interpret voluntary signals as certification risks undermining both the legal structure of open source licensing and the intent of the CRA. From a regulatory perspective, oversight remains focused on products placed on the market rather than upstream development processes. As a result, any security signals published by projects function as inputs into downstream evaluation, not as regulatory objects in themselves.

Within this framework, upstream security signals serve only as inputs into downstream due diligence. Manufacturers remain responsible for evaluating those inputs and making risk-based decisions. The availability of better signals can improve that process, but it does not shift accountability or create dependencies on upstream participation.

At the same time, the CRA introduces an important change in incentives. Manufacturers can no longer rely on passive consumption of open source components without understanding their security implications. When gaps in security signals are identified, the most effective response is not to request formal assurances but to improve the upstream ecosystem through tooling, documentation, funding, or engineering contributions. This includes supporting SBOM generation, provenance tooling, vulnerability disclosure processes, or automation of security pipelines.

This dynamic creates an opportunity for a more balanced and sustainable relationship between upstream and downstream actors. By investing in the security and transparency of the projects they depend on, manufacturers not only support their own compliance efforts but also strengthen the resilience of the broader ecosystem. This shift does not alter legal responsibilities, but it encourages a model of shared interest where better upstream practices benefit all participants without imposing new obligations on open source maintainers. 

Building a Scalable Model for Cyber Resilience

Modern software systems routinely incorporate thousands of independently evolving components, making static documentation obsolete almost as soon as it is produced. In this context, scalable due diligence cannot rely on manual, document-driven approaches. Machine-readable security signals provide a scalable alternative: continuously generated, verifiable, and aligned with dynamic software supply chains.

A scalable due diligence model therefore depends not only on machine-readable signals, but also on correctly interpreting their nature. They are evidence of behavior, not guarantees of outcome. Maintaining the distinction between transparency and assurance is what allows these signals to be useful without distorting responsibility or imposing unintended obligations upstream. 

The CRA establishes a clear downstream responsibility model, but its effectiveness depends on implementation. When grounded in automation, interoperability, and continuously updated evidence, due diligence becomes operational rather than procedural. This approach builds on existing engineering practices and widely adopted tooling, enabling scalable risk assessment without imposing new burdens on upstream maintainers. This direction is consistent with ENISA’s Security by Design and Default Playbook, which emphasizes machine-readable security attestations as a foundation for demonstrable and continuously verifiable security across the software lifecycle.

Crucially, this model preserves the sustainability of the open source ecosystem. It avoids shifting liability or compliance expectations onto maintainers, while still improving transparency through low-friction, machine-readable signals. Much of the required information already exists within projects today; the challenge is not creation, but integration and consistent reuse. By treating compliance as something assembled from technical evidence rather than declared through static attestations, the process remains both accurate and adaptable over time.

Ultimately, a shift toward continuous, evidence-based due diligence ensures cybersecurity can scale alongside software complexity. It enables manufacturers to manage large dependency landscapes efficiently, supports ecosystem resilience, and fosters more meaningful upstream–downstream collaboration. Compliance is not a one-time declaration but an ongoing capability that strengthens both regulatory outcomes and the integrity of the digital infrastructure.

About the Author

Madalin Neag works as an EU Policy Advisor at OpenSSF focusing on cybersecurity and open source software. He bridges OpenSSF (and its community), other technical communities, and policymakers, helping position OpenSSF as a trusted resource within the global and European policy landscape. His role is supported by a technical background in R&D, innovation, and standardization, with a focus on openness and interoperability.