What is the difference between code signing and software attestations?

Code signing proves that a private key signed an artifact, while software attestations also record claims about the artifact and the build that produced it. Attestations can include provenance, approvals, and build metadata, giving teams evidence about how software was created. That extra context helps consumers decide whether the artifact came from the expected process.

What code signing proves, and what it does not

code signing is primarily about authenticity and tamper evidence. A valid signature tells the verifier that a trusted private key signed the artifact and that the artifact has not been altered since signing. It does not, by itself, explain how the software was built, what source it came from, or whether the build pipeline followed an approved process.

That distinction matters because many teams use signatures as a binary trust check and stop there. In practice, a signed binary can still be poorly built, copied from an unexpected environment, or produced with weak release controls. If the only question is, “Was this artifact signed by the expected key?”, code signing answers it. If the question is, “Was it built the right way?”, code signing is incomplete.

A useful way to think about it is that the signature protects the artifact itself, while the signing key becomes the trust anchor. That makes key protection, certificate lifecycle, and signing policy central to the control. For teams managing software delivery risk, the key issue is not whether signing exists, but whether the signing identity and its usage are tightly controlled.

What attestations add: provenance, process, and context

Software attestations extend the trust picture by attaching claims about the artifact and the build that produced it. Those claims can include provenance, build metadata, approvals, dependency information, and other evidence that helps a consumer evaluate how the software was produced. In other words, attestations answer not only “who signed this?” but also “what happened before it reached me?”

This added context is valuable because supply-chain trust usually fails in the gap between source, build, and release. A signature can confirm integrity at the final checkpoint, but it does not tell you whether the artifact came from the expected source branch, whether the build ran in the approved system, or whether the release met your policy. Attestations are the mechanism that carry those extra claims forward in a verifiable form.

For practitioners, the practical difference is scope. Code signing is a narrow integrity control over the delivered object. Attestation is a broader evidence layer that supports provenance checking, release validation, and downstream policy decisions. That is why frameworks such as SLSA and the NIST AI Risk Management Framework are often discussed alongside attestations when organisations care about trustworthy build evidence and supply-chain assurance.

Risk and Threat Considerations

Code signing without attestations can create a false sense of assurance, because the consumer may trust the signer while remaining blind to the build path, approval path, or source integrity. That gap becomes material when release pipelines are compromised, keys are abused, or unsigned build steps introduce unverified content into the final artifact.

Failure mechanism: An attacker or compromised pipeline can produce an artifact that still looks legitimate at the signature layer, especially if the signing process is separated from build integrity evidence or the signing key is insufficiently protected. Without attestations, defenders may have no verifiable record of how the artifact was created, only that it was signed at some point.

Impact: Consumers may deploy software that appears trusted but lacks trustworthy provenance, which raises the risk of supply-chain compromise, unauthorized changes, and release acceptance based on incomplete evidence. This is where attestation standards and supply-chain controls, including OWASP NHI Top 10 style governance around machine trust and signing material, become relevant to release security decisions.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.

Framework	Control / Reference	Relevance
CIS Controls v8	CIS 16 — Application Software Security	Secures software integrity and release controls for signed artifacts and build evidence.
Recommendation — Enforce secure build and release controls for artifacts, signatures, and provenance evidence.
NIST CSF 2.0	PR.DS-6 — Data-at-rest is protected	Supports integrity protection for released software and associated build evidence.
	PR.IP-1 — Configuration management policies and processes are established	Applies to controlled build and release processes that attestations document.
	PR.PT-1 — Audit/log records are determined, documented, implemented, and reviewed	Attestations add evidence that complements auditability of the software supply chain.
Recommendation — Protect released artifacts and associated trust metadata from unauthorized alteration. Define and follow controlled build and release processes that produce verifiable attestations. Record and review evidence needed to trace software from build to release.

Practitioner Guidance

What to verify: Treat signature verification as the first gate, not the whole trust decision. Then verify whether the artifact carries attestations that bind it to the expected source, build system, and release workflow, because that is what closes the provenance gap.

Decision rule: If you need only tamper evidence for a known artifact, code signing may be enough. If you need to answer whether the artifact was built from the expected inputs in the expected pipeline, require attestations and make them part of release acceptance.

What good looks like: A consumer can validate the signature, inspect the attestation, and trace the artifact back to a build process that is consistent with policy. In mature environments, the signature proves integrity while the attestation proves context, and both are checked before deployment.

Practitioner takeaway: Code signing secures the object you receive, but attestations secure the story of how that object was produced, and that story is often what determines whether the artifact is trustworthy enough to deploy.