Signature trust rollover: rotate verification roots without disabling admission

Last updated: 1 Oct 20266 min read

tutorial

An artifact signature is useful only when a verifier accepts the right signer, issuer, trust root, and artifact digest. Rotating a signing key or identity-provider certificate can strand valid releases if admission trusts only the old material; trusting both indefinitely leaves an obsolete authority active. The verification policy, signing job, and deployment admission path must move in a coordinated window.

Operational decision

A payment service moves its build signer to a new identity. First inventory every verifier in CI, admission, and disaster recovery, including offline environments. Add the new trusted identity or root while retaining the old one for a bounded overlap, then sign a disposable image digest with the new path and verify it through each gate. The text contract keeps the transition reviewable. Reject a signature from an unrelated identity and reject a valid signature over a different digest. Promote one new-signed canary, check its running digest, then retire the old signer and remove old trust after all required rollback artifacts have either been re-signed under an approved path or have an explicit exception with expiry. If a signing service is unavailable during a rollout, pause promotion; do not turn verification off globally. Record which verifier accepted each release and how its trust material was distributed.

Payment signer rollover
Phase 1: inventory CI, admission, and recovery verifiers
Phase 2: trust old and new identities for a bounded window
Phase 3: verify new-signed canary digest; reject wrong signer and digest
Phase 4: move rollback inventory or issue narrow exception
Phase 5: remove old trust and test old-signer denial

Cost and verification

Running two trusted paths temporarily increases the number of credentials that can authorize a release. Removing the old path too soon can make rollback impossible. Each verifier update costs deployment and test time, especially in disconnected clusters. Monitor signature failures by reason rather than only a pass rate. Trust-root updates must be distributed through an authenticated channel; a fetched root from the same untrusted artifact being verified is circular trust.

Common Mistakes

Do not disable admission verification when one signer becomes unavailable.
Do not keep the old signer trusted forever after the migration.
Do not accept a correct signer attached to the wrong digest.

Connected lessons

Practice and check

Supply evidence follow-up

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