Turns on a client-side encryption key pair that was turned off. The key pair becomes active again for any associated client-side encryption identities. For administrators managing identities and keypairs for users in their organization, requests require authorization with a service account that has domain-wide delegation authority to impersonate users with the https://www.googleapis.com/auth/gmail.settings.basic scope. For users managing their own identities and keypairs, requests require hardware key encryption turned on and configured.