What is Code Signing?

Code signing is a security practice used to verify the authenticity and integrity of software. It allows users and systems to confirm that code was produced by a known publisher and has not been altered since it was signed. This assurance is critical in modern software delivery, where applications are distributed through automated pipelines and updated frequently.

As software supply chains grow more complex, trust becomes harder to establish. Code signing provides a cryptographic way to establish that trust, helping prevent tampering, unauthorized modifications, and the distribution of malicious software.

How Code Signing Works in Practice

At a technical level, code signing uses public key cryptography. A software publisher signs code using a private key, and anyone who receives that software can verify the signature using the corresponding public key. If the code is modified after signing, the verification fails.

In real-world workflows, the code signing process is embedded into build and release pipelines. Once code is compiled and packaged, signing occurs before artifacts are published or deployed. Operating systems, package managers, and runtime environments then verify signatures automatically before allowing execution or installation.

This process ensures three things:

• Authenticity: The software came from the claimed publisher
• Integrity: The code has not been modified after signing
• Accountability: Signed artifacts can be traced back to a specific entity

Because signing happens late in the build process, it reflects the final state of the software that users actually run.

How Code Signing Ensures Software Authenticity and Integrity

Code signing protects against a range of threats that exploit trust in software distribution. Without signing, attackers can inject malicious code into binaries, installers, or updates and distribute them as legitimate software.

When code signing is enforced:

• Modified binaries fail verification checks
• Unauthorized updates are rejected by clients
• Users receive warnings when software cannot be trusted

This protection extends beyond end users. Internal systems also rely on software signing to validate artifacts moving between environments. This is especially important in automated pipelines, where human review is limited, and trust decisions must be made programmatically.

Code signing is a core control within broader software supply chain risk management efforts, including approaches associated with software supply chain risk management. By ensuring only trusted artifacts flow through the pipeline, teams reduce the risk that upstream compromises propagate into production.

Key Steps in the Code Signing Process

The code signing process follows a defined sequence that must be handled carefully to maintain trust.

• Key generation and protection: Publishers generate cryptographic key pairs and protect private keys using hardware security modules or secure key vaults. Key compromise undermines the entire trust model.
• Certificate issuance: A trusted certificate authority verifies the publisher’s identity and issues a signing certificate. Different validation levels determine how much identity assurance is provided.
• Artifact signing: During the build or release stage, software artifacts are signed using the private key. This may include binaries, installers, containers, or update packages.
• Verification at consumption: Operating systems, deployment tools, or runtime environments verify the signature before allowing execution. Invalid or missing signatures trigger warnings or blocking behavior.
• Ongoing key and certificate management: Keys and certificates are rotated, revoked, or renewed over time to limit exposure and maintain trust.

These steps must be automated and auditable to scale safely.

Code Signing in CI/CD and Modern Delivery Pipelines

In modern environments, code signing is inseparable from CI/CD automation. Manual signing introduces delays and increases the risk of error. Automated signing ensures that every artifact produced follows the same trust rules.

When integrated correctly, code signing supports secure release workflows without slowing development. Pipelines can enforce policies that block unsigned artifacts and ensure that only verified software progresses through environments.

This integration is particularly important as teams work to avoid becoming the source of downstream compromise. Secure delivery practices that include signing align with established SDLC security practices, where trust and verification are enforced continuously rather than retroactively.

Related Content: Secure Your SDLC to Avoid Being the Source of a Supply Chain Attack

Code Signing and Supply Chain Threats

Many high-profile supply chain attacks exploit weaknesses in software distribution. Attackers target build systems, artifact repositories, or update mechanisms to insert malicious code that appears legitimate.

Code signing helps defend against these scenarios by making tampering visible. Even if attackers gain access to distribution channels, they cannot produce valid signatures without the private key.

This protection becomes more effective when combined with additional controls such as dependency verification and artifact provenance tracking. Discussions around preventing widespread compromise often highlight the importance of signed artifacts in strategies designed to prevent the next supply chain attack.

Related Content: Supply Chain Attack Lessons Learned From the tj-actions/changed-files Incident

Code Signing and Vulnerability Management

While code signing does not prevent vulnerabilities from existing, it plays an important role in controlling how vulnerable software is distributed and updated. Signed updates ensure that fixes come from trusted sources and cannot be replaced with malicious payloads.

This relationship becomes clearer when teams manage vulnerabilities across dependencies and third-party components. Vulnerabilities introduced through open source libraries are easier to manage when update mechanisms rely on signed and verified artifacts.

Code signing does not replace scanning or testing, but it strengthens the integrity of the remediation process.

Related Content: How to Mitigate SCA Vulnerabilities and Strengthen Your Supply Chain Security

Code Signing and SBOM Alignment

As organizations adopt SBOM practices, code signing adds another layer of assurance. An SBOM lists what components exist, while signing verifies that the delivered artifact matches what was built.

When combined, these practices help teams answer both “what is inside this software?” and “can I trust what I am running?” SBOM-driven visibility, paired with signed artifacts, supports stronger verification workflows and structured inventories like an SBOM. 

Related Content: The Practical Guide to SBOMs

FAQs

What are the differences between standard and extended validation code signing?

Standard validation confirms control over a domain or organization. Extended validation requires deeper identity verification, providing stronger assurance about the publisher behind the signed software.

How does code signing fit into CI/CD automation?

Code signing is automated as part of build or release stages. Pipelines sign artifacts before publication and enforce verification rules to block unsigned or modified outputs.

What are the risks of distributing unsigned or improperly signed software?

Unsigned software can be modified without detection. Improper signing erodes trust, increases the risk of malware distribution, and may trigger execution warnings or blocks in modern platforms.