Every agent-infrastructure paper lists "key rotation" beside "revocation" as a thing that must happen in under a second. The faster fix is to make rotation not matter.
Day 4 of 21 · The missing layer
In most designs the agent's identity is a key. Rotate the key and every credential, grant and registry entry that named it must be re-issued. That is why rotation is slow, and why it is dangerous: the re-issue window is where impersonation lives.
In our substrate a key is a control credential beneath the anchor. Passkeys, hardware wallets, SIWE EOAs, KMS session keys — all are facets that may sign for the account. They are added, replaced and removed under the account's custody policy: a trustee quorum, a guardian quorum, multi-credential self-recovery, or a multi-sig. The account address — the identity — never changes.
Three consequences:
- Delegations survive rotation. A grant is issued by the account, not by a key. Lose your passkey, recover with guardians, and every delegation you issued last month is still valid — and still revocable by you.
- Recovery is governance, not delegation. Adding or replacing a credential is a custody-policy operation with its own quorum. It is never expressed as "delegate to the new key," because that would let a delegation change who the principal is.
- A compromised key is not a compromised agent. Revoke the credential under custody policy. The anchor, its names, its grants and its history are untouched.
The service-agent case is stricter still (Day 10): a relying service never holds a credential of the identity it acts as — only a narrow, revocable delegation to its own session key.
Where this sits against the field: OAuth rotates by re-issuing tokens; X.509 by re-issuing certificates; NANDA by re-issuing short-lived credentials. All three re-issue because the credential is the identity.
The line: nothing in the system names the key, so nothing has to be re-signed when the key changes.
Honest limit: custody policies, guardian recovery and credential replacement are live. A public runbook of recovery drills with timings is something we still owe.
Question: In your stack, what breaks when you rotate an agent's signing key — and who has to re-sign?
#AgentIdentity #AccountAbstraction #KeyManagement #ZeroTrust #AgenticWeb
Previously: Day 3 — Everything else is a projection. Next: Day 5 — Person, organization, service.