Set up Customer Key
With Customer Key, you control your organization's encryption keys and then configure Microsoft 365 to use them to encrypt your data at rest in Microsoft's data centers. In other words, Customer Key allows customers to add a layer of encryption that belongs to them, with their keys.
Set up Azure before you can use Customer Key. This article describes the steps you need to follow to create and configure the required Azure resources and then provides the steps for setting up Customer Key. After you set up Azure, you determine which policy, and therefore, which keys, to assign to encrypt data across various Microsoft 365 workloads in your organization. For more information about Customer Key, or for a general overview, see Service encryption with Microsoft Purview Customer Key.
We strongly recommend that you follow the best practices in this article. These are called out as TIP and IMPORTANT. Customer Key gives you control over root encryption keys whose scope can be as large as your entire organization. This means that mistakes made with these keys can have a broad impact and may result in service interruptions or irrevocable loss of your data.
If you're not an E5 customer, you can try all the premium features in Microsoft Purview for free. Use the 90-day Purview solutions trial to explore how robust Purview capabilities can help your organization manage data security and compliance needs. Start now at the Microsoft Purview compliance portal trials hub. Learn details about signing up and trial terms.
Before you set up Customer Key
Before you get started, ensure that you have the appropriate Azure subscriptions and M365/O365 licensing for your organization. You must use paid Azure Subscriptions. Subscriptions you got through Free, Trial, Sponsorships, MSDN Subscriptions, and those under Legacy Support are not eligible.
Valid M365/O365 licenses that offer M365 Customer Key are:
- Office 365 E5
- Microsoft 365 E5
- Microsoft 365 E5 Compliance
- Microsoft 365 E5 Information Protection & Governance SKUs
- Microsoft 365 Security and Compliance for FLW
Existing Office 365 Advanced Compliance licenses will continue to be supported.
If you need more support beyond the documentation, contact Microsoft Consulting Services (MCS), Premier Field Engineering (PFE), or a Microsoft partner for assistance. To provide feedback on Customer Key, including the documentation, send your ideas, suggestions, and perspectives to firstname.lastname@example.org.
Overview of steps to set up Customer Key
To set up Customer Key, complete these tasks in the listed order. The rest of this article provides detailed instructions for each task, or links out to more information for each step in the process.
In Azure and Microsoft FastTrack:
You'll complete most of these tasks by remotely connecting to Azure PowerShell. For best results, use version 4.4.0 or later of Azure PowerShell.
This registration process will take five business days to complete.
Complete tasks in Azure Key Vault and Microsoft FastTrack for Customer Key
Complete these tasks in Azure Key Vault. You'll need to complete these steps for all DEPs you use with Customer Key.
Create two new Azure subscriptions
Customer Key requires two Azure subscriptions. As a best practice, Microsoft recommends that you create new Azure subscriptions for use with Customer Key. Azure Key Vault keys can only be authorized for applications in the same Azure Active Directory (Microsoft Azure Active Directory) tenant, you must create the new subscriptions using the same Azure AD tenant used with your organization where the DEPs will be assigned. For example, using your work or school account that has global administrator privileges in your organization. For detailed steps, see Sign up for Azure as an organization.
Customer Key requires two keys for each data encryption policy (DEP). In order to achieve this, you must create two Azure subscriptions. As a best practice, Microsoft recommends that you have separate members of your organization configure one key in each subscription. You should only use these Azure subscriptions to administer encryption keys for Office 365. This protects your organization in case one of your operators accidentally, intentionally, or maliciously deletes or otherwise mismanages the keys for which they are responsible.
There is no practical limit to the number of Azure subscriptions that you can create for your organization. Following these best practices will minimize the impact of human error while helping to manage the resources used by Customer Key.
Submit a request to activate Customer Key for Office 365
Once you've created the two new Azure subscriptions, you'll need to submit the appropriate Customer Key offer request in the Microsoft FastTrack portal. The selections that you make in the offer form about the authorized designations within your organization are critical and necessary for completion of Customer Key registration. The officers in those selected roles within your organization ensure the authenticity of any request to revoke and destroy all keys used with a Customer Key data encryption policy. You'll need to do this step once for each Customer Key DEP type that you intend to use for your organization.
The FastTrack team doesn't provide assistance with Customer Key. Office 365 simply uses the FastTrack portal to allow you to submit the form and to help us track the relevant offers for Customer Key. Once you've submitted the FastTrack request, reach out to the corresponding Customer Key onboarding team to start the onboarding process.
To submit an offer to activate Customer Key, complete these steps:
Using a work or school account that has global administrator permissions in your organization, sign in to the Microsoft FastTrack portal.
Once you're logged in, select the appropriate domain.
For the selected domain, choose Deploy from the top navigation bar, and review the list of available offers.
Choose the information card for the offer that applies to you:
Multiple Microsoft 365 workloads: Choose the Request encryption key help for Microsoft 365 offer.
Exchange Online and Skype for Business: Choose the Request encryption key help for Exchange offer.
SharePoint Online, OneDrive, and Teams files: Choose the Request encryption key help for SharePoint and OneDrive for Business offer.
Once you've reviewed the offer details, choose Continue to step 2.
Fill out all applicable details and requested information on the offer form. Pay particular attention to your selections for which officers of your organization you want to authorize to approve the permanent and irreversible destruction of encryption keys and data. Once you've completed the form, choose Submit.
Register Azure subscriptions to use a mandatory retention period
The temporary or permanent loss of root encryption keys can be disruptive or even catastrophic to service operation and can result in data loss. For this reason, the resources used with Customer Key require strong protection. All the Azure resources that are used with Customer Key offer protection mechanisms beyond the default configuration. You can tag or register Azure subscriptions for a mandatory retention period. A mandatory retention period prevents immediate and irrevocable cancellation of your Azure subscription. The steps required to register Azure subscriptions for a mandatory retention period require collaboration with the Microsoft 365 team. Previously, mandatory retention period was sometimes referred to as "Do Not Cancel". This process will take five business days to complete.
Before contacting the Microsoft 365 team, you must do the following steps for each Azure subscription that you use with Customer Key. Ensure that you have the Azure PowerShell Az module installed before you start.
Sign in with Azure PowerShell. For instructions, see Sign in with Azure PowerShell.
Run the Register-AzProviderFeature cmdlet to register your subscriptions to use a mandatory retention period. Complete this action for each subscription.
Set-AzContext -SubscriptionId <SubscriptionId> Register-AzProviderFeature -FeatureName mandatoryRetentionPeriodEnabled -ProviderNamespace Microsoft.Resources
Contact the corresponding Microsoft alias to proceed with the process
Before contacting the corresponding Microsoft alias, verify that you have complete your FastTrack requests for M365 Customer Key.
For enabling Customer Key for assigning DEP to individual Exchange Online mailboxes, contact email@example.com.
For enabling Customer Key for assigning DEPs to encrypt SharePoint Online and OneDrive for Business content (including Teams files) for all tenant users, contact firstname.lastname@example.org.
For enabling Customer Key for assigning DEPs to encrypt content across multiple Microsoft 365 workloads (Exchange Online, Teams, Microsoft Purview Information Protection) for all tenant users, contact email@example.com.
Include the following information in your email:
Subject: Customer Key for <Your tenant's fully qualified domain name>
Body: Include the FastTrack Request IDs and subscription IDs for each of the Customer Key services that you would like to be onboard to. These subscription IDs are the ones that you want to complete the mandatory retention period and the output of Get-AzProviderFeature for each subscription.
The Service Level Agreement (SLA) for completion of this process is five business days once Microsoft has been notified (and verified) that you have registered your subscriptions to use a mandatory retention period.
Verify the status of each your Azure Subscriptions
Once you receive notification from Microsoft that registration is complete, verify the status of your registration by running the Get-AzProviderFeature command as follows. If verified, the Get-AzProviderFeature command returns a value of Registered for the Registration State property. Complete this step for each subscription.
Get-AzProviderFeature -ProviderNamespace Microsoft.Resources -FeatureName mandatoryRetentionPeriodEnabled
Before moving on, make sure the 'RegistrationState' is set to 'Registered' like the image below.
Create a premium Azure Key Vault in each subscription
The steps to create a key vault are documented in Getting Started with Azure Key Vault, which guides you through installing and launching Azure PowerShell, connecting to your Azure subscription, creating a resource group, and creating a key vault in that resource group.
When you create a key vault, you must choose a SKU: either Standard or Premium. The Standard SKU allows Azure Key Vault keys to be protected with software - there's no Hardware Security Module (HSM) key protection - and the Premium SKU allows the use of HSMs for protection of Key Vault keys. Customer Key accepts key vaults that use either SKU, though Microsoft strongly recommends that you use only the Premium SKU. The cost of operations with keys of either type is the same, so the only difference in cost is the cost per month for each HSM-protected key. See Key Vault pricing for details.
Use the Premium SKU key vaults and HSM-protected keys for production data, and only use Standard SKU key vaults and keys for testing and validation purposes.
For each Microsoft 365 service with which you will use Customer Key, create a key vault in each of the two Azure subscriptions that you created. For example, to enable Customer Key to use DEPs for Exchange Online, SharePoint Online, and multi-workload scenarios, you'll create three pairs of key vaults.
Use a naming convention for key vaults that reflects the intended use of the DEP with which you will associate the vaults. See the Best Practices section below for naming convention recommendations.
Create a separate, paired set of vaults for each data encryption policy. For Exchange Online, the scope of a data encryption policy is chosen by you when you assign the policy to mailbox. A mailbox can have only one policy assigned, and you can create up to 50 policies. The scope of a SharePoint Online policy includes all of the data within an organization in a geographic location, or geo. The scope for a multi-workload policy includes all of the data across the supported workloads for all users.
The creation of key vaults also requires the creation of Azure resource groups, since key vaults need storage capacity (though small) and Key Vault logging, if enabled, also generates stored data. As a best practice Microsoft recommends using separate administrators to manage each resource group, with the administration that's aligned with the set of administrators that will manage all related Customer Key resources.
Assign permissions to each key vault
You'll need to define three separate sets of permissions for each key vault, depending on your implementation. For example, you will need to define one set of permissions for each of the following:
Key vault administrators that do day-to-day management of your key vault for your organization. These tasks include backup, create, get, import, list, and restore.
The set of permissions assigned to key vault administrators does not include the permission to delete keys. This is intentional and an important practice. Deleting encryption keys is not typically done, since doing so permanently destroys data. As a best practice, do not grant this permission to key vault administrators by default. Instead, reserve this for key vault contributors and only assign it to an administrator on a short term basis once a clear understanding of the consequences is understood.
To assign these permissions to a user in your organization, sign in to your Azure subscription with Azure PowerShell. For instructions, see Sign in with Azure PowerShell.
- Run the Set-AzKeyVaultAccessPolicy cmdlet to assign the necessary permissions.
Set-AzKeyVaultAccessPolicy -VaultName <vault name> -UserPrincipalName <UPN of user> -PermissionsToKeys create,import,list,get,backup,restore
Set-AzKeyVaultAccessPolicy -VaultName Contoso-CK-EX-NA-VaultA1 -UserPrincipalName firstname.lastname@example.org -PermissionsToKeys create,import,list,get,backup,restore
Key vault contributors that can change permissions on the Azure Key Vault itself. You'll need to change these permissions as employees leave or join your team. In the rare situation that the key vault administrators legitimately need permission to delete or restore a key you'll also need to change the permissions. This set of key vault contributors needs to be granted the Contributor role on your key vault. You can assign this role by using Azure Resource Manager. For detailed steps, see Use Role-Based Access Control to manage access to your Azure subscription resources. The administrator who creates a subscription has this access implicitly, and the ability to assign other administrators to the Contributor role.
Permissions to Microsoft 365 applications for every key vault that you use for Customer Key, you need to give wrapKey, unwrapKey, and get permissions to the corresponding Microsoft 365 Service Principal.
To give permission to Microsoft 365 Service Principal, run the Set-AzKeyVaultAccessPolicy cmdlet using the following syntax:
Set-AzKeyVaultAccessPolicy -VaultName <vault name> -PermissionsToKeys wrapKey,unwrapKey,get -ServicePrincipalName <Office 365 appID>
- vault name is the name of the key vault you created.
- For Exchange Online and Skype for Business, replace Office 365 appID with
- For SharePoint Online, OneDrive for Business, and Teams files, replace Office 365 appID with
- For multi-workload policy (Exchange, Teams, Microsoft Purview Information Protection) that applies to all tenant users, replace Office 365 appID with
Example: Setting permissions for Exchange Online and Skype for Business:
Set-AzKeyVaultAccessPolicy -VaultName Contoso-CK-EX-NA-VaultA1 -PermissionsToKeys wrapKey,unwrapKey,get -ServicePrincipalName 00000002-0000-0ff1-ce00-000000000000
Example: Setting permissions for SharePoint Online, OneDrive for Business, and Teams files:
Set-AzKeyVaultAccessPolicy -VaultName Contoso-CK-SP-NA-VaultA1 -PermissionsToKeys wrapKey,unwrapKey,get -ServicePrincipalName 00000003-0000-0ff1-ce00-000000000000
Confirm Get, wrapKey, and unwrapKey are granted to each key vault by running the Get-AzKeyVault cmdlet.
Get-AzKeyVault -VaultName <vault name> | fl
Before moving on, make sure the permissions are configured properly for the key vault, the Permissions to Keys will return wrapKey, unwrapKey, get. Make sure to correct the permissions to the correct service you are onboarding to. The Display Name for each service is listed below:
- Exchange Online and Skype for Business: Office 365 Exchange Online
- SharePoint Online, OneDrive, and Teams files: Office 365 SharePoint Online
- Multiple Microsoft 365 workloads: M365DataAtRestEncryption
For example, the snippet below is an example of making sure the permissions are configured for M365DataAtRestEncryption. The below cmdlet with a vault named mmcexchangevault will display the following fields.
Get-AzKeyVault -VaultName mmcexchangevault | fl
Make sure soft delete is enabled on your key vaults
When you can quickly recover your keys, you are less likely to experience an extended service outage due to accidentally or maliciously deleted keys. Enable this configuration, referred to as Soft Delete, before you can use your keys with Customer Key. Enabling Soft Delete allows you to recover keys or vaults within 90 days of deletion without having to restore them from backup.
To enable Soft Delete on your key vaults, complete these steps:
Sign in to your Azure subscription with Windows PowerShell. For instructions, see Sign in with Azure PowerShell.
Run the Get-AzKeyVault cmdlet. In this example, vault name is the name of the key vault for which you're enabling soft delete:
$v = Get-AzKeyVault -VaultName <vault name> $r = Get-AzResource -ResourceId $v.ResourceId $r.Properties | Add-Member -MemberType NoteProperty -Name enableSoftDelete -Value 'True' Set-AzResource -ResourceId $r.ResourceId -Properties $r.Properties
Confirm soft delete is configured for the key vault by running the Get-AzKeyVault cmdlet. If soft delete is configured properly for the key vault, then the Soft Delete Enabled property returns a value of True:
Get-AzKeyVault -VaultName <vault name> | fl
Before moving on, make sure the 'Soft Delete Enabled?' is set to 'True' like the image below.
Add a key to each key vault either by creating or importing a key
There are two ways to add keys to an Azure Key Vault; you can create a key directly in Key Vault, or you can import a key. Creating a key directly in Key Vault is less complicated, but importing a key provides total control over how the key is generated. Use the RSA keys. Azure Key Vault doesn't support wrapping and unwrapping with elliptical curve keys.
For instructions to add a key to each vault, see Add-AzKeyVaultKey.
For detailed steps to create a key on-premises and import it into your key vault, see How to generate and transfer HSM-protected keys for Azure Key Vault. Use the Azure instructions to create a key in each key vault.
Verify expiration date of your keys
To verify that an expiration date isn't set for your keys, run the Get-AzKeyVaultKey cmdlet as follows:
Get-AzKeyVaultKey -VaultName <vault name>
Customer Key can't use an expired key. Operations attempted with an expired key will fail, and possibly result in a service outage. We strongly recommend that keys used with Customer Key don't have an expiration date. An expiration date, once set, cannot be removed, but can be changed to a different date. If a key must be used that has an expiration date set, change the expiration value to 12/31/9999. Keys with an expiration date set to a date other than 12/31/9999 won't pass Microsoft 365 validation.
To change an expiration date that has been set to any value other than 12/31/9999, run the Update-AzKeyVaultKey cmdlet as follows:
Update-AzKeyVaultKey -VaultName <vault name> -Name <key name> -Expires (Get-Date -Date "12/31/9999")
Don't set expiration dates on encryption keys you use with Customer Key.
Check the recovery level of your keys
Microsoft 365 requires that the Azure Key Vault subscription is set to Do Not Cancel and that the keys used by Customer Key have soft delete enabled. You can confirm you subscriptions settings by looking at the recovery level on your keys.
To check the recovery level of a key, in Azure PowerShell, run the Get-AzKeyVaultKey cmdlet as follows:
(Get-AzKeyVaultKey -VaultName <vault name> -Name <key name>).Attributes
Before moving on, If the Recovery Level property returns anything other than a value of Recoverable+ProtectedSubscription, ensure that you have registered the MandatoryRetentionPeriodEnabled feature on the subscription and that you have soft delete enabled on each of your key vaults.
Back up Azure Key Vault
Immediately following creation or any change to a key, perform a backup and store copies of the backup, both online and offline. To create a backup of an Azure Key Vault key, run the Backup-AzKeyVaultKey cmdlet.
Obtain the URI for each Azure Key Vault key
Once you've set up your key vaults and added your keys, run the following command to get the URI for the key in each key vault. You'll use these URIs when you create and assign each DEP later, so save this information in a safe place. Run this command once for each key vault.
In Azure PowerShell:
(Get-AzKeyVaultKey -VaultName <vault name>).Id
Once you've completed the steps in this article, you're ready to create and assign DEPs. For instructions, see Manage Customer Key.
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