Microsoft Double Key Encryption (DKE) Resources

CCKM provides support for Double Key Encryption (DKE) for Microsoft 365. With DKE, two keys are used to access content (such as files or documents) that is protected with the sensitivity labels that you apply when using any one of the supported Microsoft Office apps. You hold one key in CCKM, which you maintain full control over using the using Microsoft’s Double Key Encryption service. The other is securely stored within Microsoft Azure. To decrypt and gain access to the protected content, both keys are required. Since Microsoft holds only one of the keys, this solution ensures that Microsoft cannot independently access this content. Only your authorized users can access the protected content.

Only your highly confidential data should be protected by DKE, which is typically a small percentage of your organization’s overall data. For more information about DKE, guidance on what type of content to protect, the supported office applications, and other information, refer to Double Key Encryption.

DKE encryption workflow

1. User adds a DKE label to a document. The Microsoft Office client connects to Azure RMS (Protection Service).

2. User certificate, API templates, and Azure RMS key are sent to the Microsoft Office client.

3. Microsoft Office client requests CCKM for the DKE public key associated with the applied label.

4. CCKM verifies the request. After authorization succeeds, CCKM sends the DKE public key to the Microsoft Office client.

5. Microsoft Office client encrypts the document content with the content key.

6. Microsoft Office client encrypts the part of the metadata that controls access to the content with the DKE public key.

7. Microsoft Office client encrypts the encrypted metadata with the Azure RMS key.

The content is protected with the double-encrypted content key, RMS key and DKE public key. The following illustration shows the DKE encryption workflow:

DKE decryption workflow

1. User opens a document which has a DKE label. The Microsoft Office client first sends the double-encrypted metadata to Azure RMS (Protection Service).

2. Azure RMS (Protection Service) decrypts the double-encrypted metadata using the Azure RMS key and returns the simple-encrypted metadata.

3. Microsoft Office client sends the simple-encrypted metadata to CCKM and requests CCKM to decrypt it.

4. CCKM verifies the request and goes through the authorization process. When authorization passes successfully, CCKM decrypts the simple-encrypted metadata and returns the decrypted metadata to the Microsoft Office client.

5. Microsoft Office client uses the content key to decrypt the document. The user can view the document content.

The following illustration shows the DKE decryption workflow:

The following are the high-level steps to configure DKE within Microsoft and CipherTrust Manager/CCKM:

1. Complete the prerequisites.

2. Configure DKE on CCKM.

3. Register your DKE service from Microsoft Azure portal.

4. Create your DKE sensitivity labels from Microsoft Compliance portal.

Prerequisites

In preparation for deploying DKE, ensure that the following prerequisites are met:

1. Ensure CipherTrust Manager/CCKM is installed and running. In addition, ensure to activate and install the CCKM license. Refer to the CipherTrust Manager Deployment Guide and Licensing for details.

2. Microsoft 365 E5 License: Windows clients must have a Microsoft 365 E5 license. Refer to information about system and licensing requirements for DKE for more information these licensing requirements.

   Note

   CCKM supports built-in sensitivity labeling with Office apps. CCKM does not support Azure Information Protection unified labeling client, which is to be deprecated in the future.

3. User Presence in Azure Directory: Users who are to create and share documents or files protected by DKE must be part of the Azure Active Directory (Azure AD) associated with the organization's tenant.

   Note

   • DKE is not supported on applications running on mobile devices.

   • DKE is only tested with Windows clients. DKE is not tested with Mac, iOS, and Android clients.

   • To configure the B2B cross-tenant access settings, refer to Configure cross-tenant access settings for B2B collaboration.

Configure DKE on CCKM

To configure DKE on CCKM, do the following:

1. Install a third-party CA certificate on the web interface.

   Note

   We recommend obtaining a CA-signed certificate for the web interface from trusted CAs that are part of the Microsoft Trusted Root Program. For more information, refer to Microsoft Trusted Root Program participants.

2. From CCKM GUI or API, create a DKE endpoint. Refer to Creating Microsoft DKE Endpoints for details on how to create a DKE endpoint from CCKM GUI or Creating Microsoft DKE Endpoints using CCKM API.

   Note

   • Only Azure AD users are currently supported. The email addresses included in the API call must be associated with a user Azure AD. The email address parameter an optional field applicable only if authorization_type is set to email.

     If you specified one or more email addresses in a DKE endpoint, this field would be validated against JWT received in the decrypt operation.

   • A Microsoft Office 365 client user and email (if configured in CipherTrust Manager) must match.

   • The Issuer field must be specific to the tenant configured in the Microsoft Azure Portal.

   • The web interface port within CipherTrust Manager can be changed from the default port of 443 to another port. If you plan to change the default port for the CipherTrust Manager web interface, ensure to change it BEFORE configuring the Microsoft DKE service on CCKM. Also reflect this port change when creating a DKE endpoint on CCKM as part of the prerequisites for deploying DKE. Changing the default port AFTER configuring Microsoft DKE is not supported.

Register your DKE service

After creating a DKE endpoint, proceed to register your DKE service from the Microsoft Azure portal. Refer to Register your key store for details.

Create your DKE sensitivity labels

After successfully registering your key store, you are ready to create your DKE sensitivity labels from the Microsoft Compliance portal. Refer to Create sensitivity labels using DKE for details.

When creating a sensitivity label, ensure to do the following:

• Select Apply or remove Encryption on the protection settings for labeled items page.
• Select the Use Double Key Encryption checkbox to enable DKE on the Encryption page. Enter the the value of the key_urireceived in the API response when you created a DKE endpoint using the create DKE endpoint API.

You can manage the following DKE resources on CCKM.

• Managing DKE Endpoints

• Managing DKE Authorized Tenants