Key Rotation

Rotation covers several different operations. They should not be collapsed into one vague "rotate keys" action.

Taxonomy

Operation	What changes	Address changes
Envelope rewrap	Encryption around the same plaintext share.	No
Server internal custody rotation	How the same effective server share is protected.	No
Lane share refresh	Holder share and server share for one lane.	No
Delegated lane revocation	Lane status and server-share admission.	No
Wallet rekey	Wallet key material.	Usually yes

Ed25519 Streaming Yao participates when a lifecycle operation provisions or refreshes signing shares, activates SigningWorker material, or performs an authorized export. Envelope rewrap stays at the storage layer when the underlying share is unchanged. ECDSA follows its separate strict Router A/B threshold-PRF path.

Address-Preserving Refresh

For a two-party additive lane:

h_old + s_old = wallet_key
h_new + s_new = wallet_key
delta = h_old - h_new
s_new = s_old + delta

The new lane epoch activates only after parity verification:

H_new + S_new == existing wallet public key

Revocation has priority over rotation. A revoked lane must fail admission even if stale holder material still exists.