Even in storage, data can be vulnerable if not properly encrypted. Microsoft Azure Cosmos DB provides robust encryption capabilities, whereby you can leverage customer-managed keys (CMK) to gain higher control over your data encryption. In this article, we will delve into the significance of this capability, how to set it up, and how you can manage it effectively.
Understand Customer-Managed Keys
By default, Azure Cosmos DB encrypts your data at rest with service-managed keys. However, for those seeking more control over encryption key management, Azure Cosmos DB offers Customer Managed Keys (CMK) as an enhanced security measure. This feature allows clients to control and manage their encryption keys in the Azure portal, ensuring a more robust sense of privacy and control over their sensitive data.
It’s important to note that CMK is available for both Azure Cosmos DB’s API for MongoDB and SQL (Core) API, making it easy for experts using both technologies to implement this encryption method.
Advantages of Customer-Managed Keys
Unlike service-managed keys, customer-managed keys offer:
- Key Control: You manage and control keys in Azure Key Vault.
- Key Revocation: Ability to stop Cosmos DB from using the key in Azure Key Vault.
- Key Rotation: Enables you to rotate, roll, or expire keys at your discretion directly from Key Vault.
- Audit Trails: Microsoft provides logs on all actions and operations performed on keys in Key Vault.
Setting up Customer-Managed Keys
Before you begin, ensure that your Azure subscription includes Key Vault and Cosmos DB.
Step 1: Create or Use an Existing Key Vault and Key
In Azure Portal, you can either create a new Key Vault or use an existing one. You also need to generate or use an existing key in the Key Vault that will be used for the encryption process.
Step 2: Update Access Policies
After creating the Key Vault and Key, update the Key Vault access policy to provide Cosmos DB service certain permissions, including ‘get’, ‘wrapkey’, and ‘unwrapkey’.
Step 3: Enable the CMK on the Cosmos DB account
Next, enable CMK encryption on your Azure Cosmos DB account and provide the Key Vault and Key ID previously created.
Step 4: Validate
Finally, validate the encryption by fetching the Cosmos DB account details and confirming that the ‘keyVaultKeyUri’ value is identical to the one you inputted in Step 3.
Managing Customer-Managed keys
Managing CMK involves two crucial areas of focus: encryption status and key rotation.
- Encryption Status: You can verify your encryption status through the Azure portal, Azure CLI, or PowerShell. It’s crucial to consistently check this status to ensure your data remains protected.
- Key Rotation: As an enhanced security measure, regularly changing or ‘rotating’ keys is recommended. Azure Key Vault supports this functionality, allowing you to redefine your cryptographic keys without any interruptions to your service. During rotation, Cosmos DB continues to use the older versions of keys to decrypt data while using the latest key version for new write operations.
In conclusion, Azure Cosmos DB’s Customer Managed Keys extend your control over encryption, fostering increased data security. By managing this feature effectively and understanding its ins and outs, you can enhance the protection of your sensitive data at rest in your Cosmos DB account. Whether you’re studying for the DP-420 exam or working in a professional context, the command over CMKs that Azure Cosmos DB offers can certainly enhance your data management capabilities.
Practice Test
True or False: Azure Cosmos DB supports customer-managed keys for encrypting data at rest.
- True
- False
Answer: True
Explanation: Azure Cosmos DB provides an option for customers to manage their encryption keys, thus allowing them to encrypt their data at rest.
Which service are customer-managed keys typically stored in Microsoft Azure?
- a) Azure Key Vault
- b) Azure Active Directory
- c) Azure Blob Storage
- d) Azure Function App
Answer: a) Azure Key Vault
Explanation: Azure Key Vault is the service that securely stores and controls access to tokens, passwords, certificates, API keys, and other secrets.
True or False: Using customer-managed keys for encryption in Azure Cosmos DB has no impact on the performance of the database.
- True
- False
Answer: True
Explanation: The use of customer-managed keys for encryption has virtually no impact on the performance of Azure Cosmos DB.
When using customer-managed keys in Azure Cosmos DB, who is responsible for the key management tasks such as rotation and revocation?
- a) Microsoft
- b) The customer
- c) Both Microsoft and the customer
- d) None of the above
Answer: b) The customer
Explanation: When using customer-managed keys, the responsibility for key management tasks like key rotation and revocation lies with the customer.
Which type of Azure Cosmos DB account supports the use of customer-managed keys for encryption?
- a) Provisioned throughput accounts
- b) Database-level throughput accounts
- c) Serverless accounts
- d) All of the above
Answer: a) Provisioned throughput accounts
Explanation: As per the current Azure Cosmos DB’s capability, only provisioned throughput accounts support the use of customer-managed keys for encryption.
True or False: Customer-managed keys can be used to encrypt both data and indexes in Azure Cosmos DB.
- True
- False
Answer: True
Explanation: In Cosmos DB, you can use customer-managed keys to encrypt data and indexes.
Which of the following is not a configuration option when using customer-managed keys in Azure Cosmos DB?
- a) Enable or disable encryption
- b) Specify a key rotation schedule
- c) Revoke access to a key
- d) Specify the encryption algorithm
Answer: d) Specify the encryption algorithm
Explanation: While you can enable encryption, specify key rotation, and revoke access to keys, you cannot specify the encryption algorithm when using customer-managed keys in Azure Cosmos DB.
Can you turn off the customer-managed key feature once it is enabled for an Azure Cosmos DB account?
- a) Yes, at any time
- b) Only before any data is stored in the account
- c) Only within 30 days after enabling the feature
- d) No, it cannot be turned off
Answer: d) No, it cannot be turned off
Explanation: Once customer-managed keys are enabled for an Azure Cosmos DB account, the feature cannot be turned off.
True or False: Azure Key Vault’s managed HSM (Hardware Security Module) is supported by Cosmos DB for customer managed keys?
- True
- False
Answer: False
Explanation: Cosmos DB currently only supports standard Azure Key Vault for customer-managed keys. Managed HSM is not supported.
How many encryption keys can you configure per Cosmos DB account for customer managed keys?
- a) 1
- b) 3
- c) 5
- d) 10
Answer: a) 1
Explanation: Currently, you can only associate one Azure Key Vault key with one Cosmos DB account for customer managed keys.
What type of Azure Key Vault key is supported by Cosmos DB for customer managed keys?
- a) RSA keys
- b) EC keys
- c) Both RSA and EC keys
- d) Neither RSA nor EC keys
Answer: a) RSA keys
Explanation: Cosmos DB supports only RSA keys for customer managed keys. EC keys are not supported currently.
True or False: You can associate a customer managed key to a Cosmos DB account at the time of creation as well as after the account has been created.
- True
- False
Answer: True
Explanation: You can associate a customer managed key during the creation of a Cosmos DB account or anytime after the Cosmos DB account has been created.
How does Cosmos DB encrypt data at rest when customer-managed keys are not used?
- a) It does not encrypt data at rest
- b) With Microsoft-managed keys
- c) With a default customer key
- d) With RSA encryption
Answer: b) With Microsoft-managed keys
Explanation: By default, Cosmos DB encrypts data at rest with service-managed keys. If you don’t use customer-managed keys, Microsoft continues with its underlying encryption-at-rest process.
True or False: If a customer managed key is disabled or deleted in Azure Key Vault, Cosmos DB will continue to use the key for decryption if it was previously encrypted with the key.
- True
- False
Answer: False
Explanation: If a customer managed key is disabled or deleted in Azure Key Vault, Cosmos DB will have no access to it, so it cannot continue to use the key for decryption.
Where does the customer managed key reside?
- a) Inside the Cosmos DB
- b) In the Azure Key Vault
- c) On the customer’s local machine
- d) Azure Blob Storage
Answer: b) In the Azure Key Vault
Explanation: The customer managed key resides in the Azure Key Vault, it never leaves the vault and Cosmos DB never sees the actual encryption key.
Interview Questions
What does the term “Customer-managed keys” refer to in context of Azure Cosmos DB?
Customer-managed keys refers to the concept in Azure Cosmos DB where the customer manages the encryption keys used to encrypt the data at rest. This feature enhances the security and compliance of the application data stored in Azure Cosmos DB.
How is the customer-managed key activated for Cosmos DB?
Customer-managed key is activated for Cosmos DB through Azure Key Vault. A customer creates or imports a key into Azure Key Vault and then provides the key identifier during Cosmos DB account setup to enable encryption with a customer-managed key.
What is Azure Key Vault?
Azure Key Vault is a service provided by Azure to safeguard cryptographic keys and other secrets used by cloud apps and services. It provides the ability to store large amounts of secrets like keys in a secure and distributed manner.
Can existing Cosmos DB accounts be updated to use customer-managed keys?
No, it’s not possible to update existing Cosmos DB accounts to use customer-managed keys. It’s a feature that can only be enabled during account creation.
Can multiple Cosmos DB accounts use the same customer-managed key?
Yes, multiple Cosmos DB accounts can use the same customer-managed key. However, careful management and organization of these keys is important to maintain security.
How can you verify if your Cosmos DB account is encrypted with a customer-managed key?
You can verify this through the Azure portal. Within the settings of your Cosmos DB account, there is an option to review the Customer Managed Key properties including Key Vault details.
What is the purpose of customer-managed keys?
Customer-managed keys allow customers to have control over their encryption keys and manage the lifecycle of these keys, which enhances security compliance and provides flexibility in operational procedures.
How often does Cosmos DB rotate customer-managed keys automatically?
Cosmos DB does not rotate customer-managed keys automatically. The owners of the keys must manage the rotation and maintain its life cycle.
What happens if the Key Vault containing the customer-managed key is deleted?
If a Key Vault containing a customer-managed key is deleted, the data in the Cosmos DB account becomes read-only. To restore write functionality, a replacement key stored in Key Vault must be provided.
Can a customer-managed key be disabled without affecting the Cosmos DB account?
No, disabling a customer-managed key in Key Vault will result in making the Cosmos DB account read-only. You need to enable the key again to make the Cosmos DB account writable.
Can the data be accessed if the customer-managed key is revoked?
No, if a customer-managed key is revoked or disabled in Azure Key Vault, the Cosmos DB data it secures cannot be read or written until access to the key is restored.
How does Cosmos DB ensure the keys are secure when using customer-managed keys?
Cosmos DB never directly has access to the key. It uses Azure Key Vault’s decrypt operation, which handles the key within secure, isolated hardware to protect it. Any operation involving the key happens within the bounds of Azure Key Vault.
Can customer-managed keys be utilized for Azure Synapse Link?
Yes, you can use customer-managed keys for Azure Synapse Link, a hybrid transactional analytical processing (HTAP) capability in Azure Cosmos DB.
Can I move a customer key to a new key vault without losing access to my data?
It is not recommended to move a customer key to a new key vault. Instead, a new customer-managed key can be created in the new vault and applied to the Cosmos DB account to maintain data access.
Which encryption algorithm does Azure Cosmos DB use for customer-managed keys?
Azure Cosmos DB uses the RSA encryption algorithm for customer-managed keys.
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