Evidence of Use

Expanded Definition

Evidence of use is the verifiable record that a certificate, token, or other trust artifact was presented and accepted at a specific time, in a specific context, and by a specific identity. In NHI security, it is less about the certificate itself and more about the proof that the certificate actually drove an access, signing, or authorisation event. That makes it foundational to auditability, dispute resolution, and post-incident reconstruction. It also sits adjacent to, but is not the same as, logging, attestation, or certificate issuance records. Industry usage is still evolving, but the operational expectation is consistent with NIST Cybersecurity Framework 2.0 principles for traceability and monitoring. In practice, evidence of use should be sufficient to answer who used the certificate, what system accepted it, what action resulted, and whether the event was authorised under policy.

The most common misapplication is treating issuance logs as evidence of use, which occurs when teams can prove a certificate was created but cannot prove it was actually presented or consumed during a transaction.

Examples and Use Cases

Implementing evidence of use rigorously often introduces retention and correlation overhead, requiring organisations to weigh stronger auditability against higher logging and storage costs.

• A service account uses a client certificate to authenticate to an internal API, and the audit record ties the certificate fingerprint to the request, endpoint, and transaction outcome.
• An automated signing workflow applies a code-signing certificate during release, and the organisation preserves the event trail to show which pipeline job invoked the signer and when.
• A cross-border partner exchange uses mutual TLS, and the receiving platform records certificate subject, trust chain validation, and the business action that followed.
• An incident responder reviews whether a suspected compromised certificate was actively used, then compares gateway logs, identity telemetry, and vault history to reconstruct the access path.
• Teams investigating hard-to-trace credential abuse may correlate certificate use with patterns described in Code Formatting Tools Credential Leaks and similar NHI exposure paths.

For broader identity control design, practitioners should also align these records with the visibility expectations discussed in Ultimate Guide to NHIs and with event logging guidance in NIST Cybersecurity Framework 2.0.

Why It Matters in NHI Security

Evidence of use closes a critical gap in NHI governance: without it, organisations may know a certificate exists but still be unable to prove whether it was used legitimately, replayed, shared, or silently abused. That weakness matters because NHI environments are already marked by poor visibility and weak lifecycle control, with NHI Mgmt Group reporting that only 5.7% of organisations have full visibility into their service accounts and that 80% of identity breaches involved compromised non-human identities such as service accounts and API keys. In that context, evidence of use becomes the difference between a presumed control and a defensible control. It supports investigations, non-repudiation arguments, and compliance narratives in regulated workflows. It also helps detect hidden dependencies when certificates are embedded in automation, partner integrations, or developer tooling, as seen in cases such as JetBrains GitHub plugin token exposure and Hard-Coded Secrets in VSCode Extensions.

Organisations typically encounter the need for evidence of use only after a disputed transaction, a suspected compromise, or a regulatory request, at which point the term becomes operationally unavoidable to address.

Related resources from NHI Mgmt Group

• How should security teams use automation without weakening compliance evidence?
• How do security and compliance teams use AI observability evidence?
• How do compliance teams use PAM evidence effectively?
• How do compliance teams use runtime evidence in an audit?