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Encryption Key Management

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In this guide, you can learn how to manage your encryption keys with a Key Management System (KMS) in your Client-Side Field Level Encryption (CSFLE)-enabled application.

MongoDB uses the following components to perform Client-Side Field Level Encryption:

  • Data Encryption Keys (DEKs)
  • Key Vault collections
  • Customer Master Keys (CMKs)
  • Key Management System (KMS)

Your Data Encryption Key is the key you use to encrypt the fields in your MongoDB documents. Your DEK is stored in a document in a MongoDB collection called the Key Vault collection.

Your Customer Master Key is the key you use to encrypt your Data Encryption Keys. MongoDB automatically encrypts Data Encryption Keys using the specified CMK during Data Encryption Key creation.

The CMK is the most sensitive key in CSFLE. If your CMK is compromised, all of your encrypted data can be decrypted.

Use a Key Management System to store your Customer Master Key.

To learn more about the relationship between keys, see Keys and Key Vaults.

Important
Use a Remote Key Management Service Provider

Ensure you store your Customer Master Key (CMK) on a remote KMS.

To learn more about why you should use a remote KMS, see Reasons to Use a Remote KMS.

To view a list of all supported KMS providers, see the KMS Providers page.

Client-Side Field Level Encryption supports the following Key Management System (KMS) providers:

  • Amazon Web Services KMS
  • Azure Key Vault
  • Google Cloud Platform KMS
  • Any KMIP Compliant Key Management System
  • Local Key Provider (for testing only)

To learn more about these providers, including diagrams that show how your application uses them to perform Client-Side Field Level Encryption, see KMS Providers.

Using a remote KMS to manage your Customer Master Key (CMK) has the following advantages over using your local filesystem to host the CMK:

  • Secure storage of the key with access auditing
  • Reduced risk of access permission issues
  • Availability and distribution of the key to remote clients
  • Automated key backup and recovery
  • Centralized encryption key lifecycle management

Additionally, for the following KMS providers, your KMS remotely encrypts and decrypts your Data Encryption Key, ensuring your Customer Master Key is never exposed to your CSFLE-enabled application:

  • Amazon Web Services KMS
  • Azure Key Vault
  • Google Cloud Platform KMS

You can assign a Data Encryption Key (DEK) alternate names to make the key easier to reference. Assigning alternate names allows you to perform the following actions:

  • Reference a DEK by different means than the _id field.
  • Dynamically assign DEKs at runtime.
Important
Prerequisite

Prior to adding a new key alternate name, you must create a unique index on the keyAltNames field. Client-Side Field Level Encryption depends on server-enforced uniqueness of key alternate names.

To learn how to create a unique index, see Unique Indexes.

The following example creates a DEK with an alternate name. Select the tab that corresponds to your driver language:

To learn more about dataKeyOpts and kmsProviders objects, see KMS Providers.

Encryption schemas contain user-specified rules that identify which fields must be encrypted and how to encrypt those fields. In your encryption rules, you can specify alternate key names name for the Data Encryption Key which encrypts your field.

You must refer to a key alternate name with a JSON pointer. A JSON pointer is a string prefixed with a "/" character that can be used to access a particular field value in the same or another document. Use JSON pointers to reference a field in your query or update document which contains the value of your key alternate name.

Important
Cannot Use Alternate Name for Deterministically Encrypted Field

You cannot reference a DEK by it's alternate name when encrypting a field with the deterministic encryption algorithm. To encrypt your field deterministically, you must specify the _id of the key you would like to use to encrypt your field.

Consider the following encryption schema which encrypts the salary field:

{
"<database>.<collection>": {
"bsonType": "object",
"properties": {
"salary": {
"encrypt": {
"bsonType": "int",
"keyId": "/fieldWithAltName",
"algorithm": "AEAD_AES_256_CBC_HMAC_SHA_512-Random"
}
}
}
}
}

The schema's keyId field contains a JSON pointer to reference the fieldWithAltName field within the documents being encrypted.

The following document's fieldWithAltName value is my-alt-name:

{
"name": "Jon Doe",
"salary": 45000,
"fieldWithAltName": "my-alt-name"
}

The salary field is encrypted by the the Data Encryption Key that has the alternate name my-alt-name.

You can use alternate key names to dynamically set the Data Encryption Key for a field at runtime. Use this functionality to encrypt individual documents with different Data Encryption Keys using the same encryption schema.

For example, consider the following documents:

{
"name": "Jon Doe",
"salary": 45000,
"fieldWithAltName": "my-alt-name"
},
{
"name": "Jane Smith",
"salary": 70000,
"fieldWithAltName": "my-other-alt-name"
}

You insert the preceding documents using a CSFLE-enabled client configured with the encryption schema from the previous example.

In the encryption schema, the salary.encrypt.keyId field contains a JSON pointer to the fieldWithAltName field of the inserted document. As a result, the salary fields in the two example documents are uniquely encrypted using Data Encryption Keys specific to the individual document. The keys are assigned dynamically at runtime.

You can delete a DEK from your Key Vault collection using standard CRUD delete operations.

Tip
MongoDB Shell Specific Feature

The MongoDB shell allows you to delete a DEK by UUID using the keyVault.deleteKey() method as follows:

keyVault = db.getKeyVault()
keyVault.deleteKey(UUID("<UUID String>"))

To learn more about Key Vault collections see Key Vault Collections.

For tutorials detailing how to set up a CSFLE-enabled application with each of the supported KMS providers, see the following pages:

To view additional examples of encryption schemas, see Encryption Schemas.

←  Keys and Key VaultsFields and Encryption Types →

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