Begin by conducting a gap analysis to understand where your current software development practices stand in relation to the SSDF requirements. This involves reviewing the SSDF's practices and principles against your existing processes to identify areas for improvement. Then, develop an implementation plan that prioritizes actions based on risk, resources, and business impact.

NIST SP 800-218 outlines several key practices, including:

‍Prepare the Organization: Ensure that policies, procedures, and tools are in place to support secure software development.

‍Protect Software: Implement measures to protect software from unauthorized access and tampering throughout its lifecycle.

‍Produce Well-Secured Software: Incorporate security considerations into every stage of the development process, from design to deployment.

‍Respond to Vulnerabilities: Establish processes for identifying, assessing, and mitigating vulnerabilities in both development and post-deployment phases.

Implementing NIST SP 800-218 requires a combination of organizational policies, security tools, and training programs. Tools may include code analysis software, encryption libraries, and vulnerability scanners. Training should cover secure coding practices, threat modeling, and security testing for development teams.

SMEs can focus on prioritizing the most critical and impactful practices within the SSDF that align with their specific risks and business needs. Leveraging open-source tools, seeking external expertise through consultancy, and gradually building up security practices can make the adoption process more manageable. It’s also beneficial to integrate these practices incrementally, starting with high-priority projects.

The time required to implement NIST SP 800-218 can vary widely depending on the size of the organization, the current maturity of its software development practices, and the complexity of its projects. For some, initial steps towards compliance can be achieved within a few months, while fully integrating all aspects of the SSDF into complex environments may take several years. It's a continuous process of improvement rather than a one-time goal.

Attestation of compliance with NIST SP 800-218 involves providing evidence that your software development practices align with the guidelines set forth in the SSDF. This typically means documenting the secure development policies, procedures, and controls you have implemented, and demonstrating how they meet the framework's requirements.

The responsibility for attesting to compliance generally falls on the organization's leadership involved in software development, such as CTOs, Heads of Software Development, or DevSecOps leaders. In some cases, third-party auditors or assessors may be involved in verifying compliance.

Preparation for a compliance audit involves:

Conducting an internal review or pre-audit to identify any gaps in compliance.

Ensuring all documentation related to secure software development practices is up to date and accessible.

Training staff on their roles and responsibilities regarding SSDF compliance.

Engaging with qualified auditors to understand their requirements and expectations.

As of my last update, NIST does not mandate third-party certification for SSDF compliance. However, obtaining a third-party assessment can add credibility to your compliance claims and provide valuable insights into your security practices. It may also be required by some government contracts or industry regulations.

Challenges may include:

Resource Allocation: Ensuring sufficient resources are dedicated to compliance efforts. Address this by prioritizing activities that offer the highest security value.

‍Documentation and Evidence Gathering: Maintaining comprehensive records of compliance efforts. Implement systematic documentation practices to streamline this process.

‍Keeping Up with Evolving Standards: NIST SP 800-218 may be updated. Stay informed of changes by regularly reviewing NIST publications and adjusting your practices accordingly.

Addressing these challenges requires a proactive approach to compliance, continuous improvement of secure development practices, and engagement with the broader cybersecurity community to share insights and best practices.