This holds the security key that is actually deployed and currently protecting this controller's encrypted local drives, as opposed to any newer key staged for rotation but not yet applied. An admin compares this against the configured securityKey field specifically to detect a stalled key rotation, where a newly typed key hasn't successfully deployed to the controller yet. If deployedSecurityKey still shows the old key's hash while securityKey shows a new one, that mismatch tells the admin the rekey operation is still pending or failed.