Roll or rotate a Customer Key or an availability key
Only roll an encryption key that you use with Customer Key when your security or compliance requirements dictate that you must roll the key. In addition, do not delete any keys that are or were associated with policies. When you roll your keys, there will be content encrypted with the previous keys. For example, while active mailboxes will be re-encrypted frequently, inactive, disconnected, and disabled mailboxes may still be encrypted with the previous keys. SharePoint Online performs backup of content for restore and recovery purposes, so there may still be archived content using older keys.
About rolling the availability key
Microsoft does not expose direct control of the availability key to customers. For example, you can only roll (rotate) the keys that you own in Azure Key Vault. Office 365 rolls the availability keys on an internally-defined schedule. There is no customer-facing, service-level agreement (SLA) for these key rolls. Office 365 rotates the availability key using Office 365 service code in an automated, non-manual process. Microsoft administrators may initiate the roll process. The key is rolled using automated mechanisms without direct access to the key store. Access to the availability key secret store is not provisioned to Microsoft administrators. Availability key rolling leverages the same mechanism used to initially generate the key. For more information about the availability key, see Understand the availability key.
Exchange Online and Skype for Business availability keys can be effectively rolled by customers creating a new DEP, since a unique availability key is generated for each DEP you create. Availability keys for SharePoint Online, OneDrive for Business, and Teams files exist at the forest level and are shared across DEPs and customers, which means rolling only occurs at a Microsoft internally defined schedule. To mitigate the risk of not rolling the availability key each time a new DEP is created, SharePoint, OneDrive, and Teams roll the tenant intermediate key (TIK), the key wrapped by the customer root keys and availability key, each time a new DEP is created.
Request a new version of each existing root key you want to roll
When you roll a key, you request a new version of an existing key. To request a new version of an existing key, you use the same cmdlet, Add-AzKeyVaultKey, with the same syntax that you used to create the key in the first place. After you’ve finished rolling any key associated with a Data Encryption Policy (DEP), you run another cmdlet to ensure that Customer Key begins using the new key. Do this step in each Azure Key Vault (AKV).
Sign in to your Azure subscription with Azure PowerShell. For instructions, see Sign in with Azure PowerShell.
Run the Add-AzKeyVaultKey cmdlet as shown in the following example:
Add-AzKeyVaultKey -VaultName Contoso-O365EX-NA-VaultA1 -Name Contoso-O365EX-NA-VaultA1-Key001 -Destination HSM -KeyOps @('wrapKey','unwrapKey') -NotBefore (Get-Date -Date "12/27/2016 12:01 AM")
In this example, since a key named Contoso-O365EX-NA-VaultA1-Key001 exists in the Contoso-O365EX-NA-VaultA1 vault, the cmdlet creates a new version of the key. This operation preserves the previous key versions in the version history for the key. You need the previous key version to decrypt the data that it still encrypts. Once you complete rolling any key associated with a DEP, run an extra cmdlet to ensure that Customer Key begins using the new key. The following sections describe the cmdlets in more detail.
Update the Customer Key for Exchange Online and Skype for Business
When you roll either of the Azure Key Vault keys associated with a DEP used with Exchange Online and Skype for Business, you must update the DEP to point to the new key. This does not rotate the availability key.
To instruct Customer Key to use the new key to encrypt mailboxes in Office 365 run the Set-DataEncryptionPolicy cmdlet as follows:
Run the Set-DataEncryptionPolicy cmdlet in Azure PowerShell:
Set-DataEncryptionPolicy -Identity <DataEncryptionPolicyID> -Refresh
Within 72 hours, the active mailboxes associated with this DEP become encrypted with the new key.
To check the value for the DataEncryptionPolicyID property for the mailbox, use the steps in Determine the DEP assigned to a mailbox. The value for this property changes once the service applies the updated key.
Update the Customer Key for SharePoint Online, OneDrive for Business, and Teams files
SharePoint Online only allows you to roll one key at a time. If you want to roll both keys in a key vault, wait for the first operation to complete. Microsoft recommends that you stagger your operations to avoid this issue. When you roll either of the Azure Key Vault keys associated with a DEP used with SharePoint Online and OneDrive for Business, you must update the DEP to point to the new key. This does not rotate the availability key.
Run the Update-SPODataEncryptionPolicy cmdlet as follows:
Update-SPODataEncryptionPolicy -Identity <SPOAdminSiteUrl> -KeyVaultName <ReplacementKeyVaultName> -KeyName <ReplacementKeyName> -KeyVersion <ReplacementKeyVersion> -KeyType <Primary | Secondary>
While this cmdlet starts the key roll operation for SharePoint Online and OneDrive for Business, the action doesn't complete immediately.
To see the progress of the key roll operation, run the Get-SPODataEncryptionPolicy cmdlet as follows:
Get-SPODataEncryptionPolicy -Identity <SPOAdminSiteUrl>