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New in version 4.2.


Client-Side Field Level Encryption is available as a beta. The contents of this page may change during the beta period.


Returns the ClientEncryption object for the current database collection. The ClientEncryption object supports explicit (manual) encryption and decryption of field values for Client-Side field level encryption.

getClientEncryption() has the following syntax:

returns:The ClientEncryption object for current database connection.

Use the ClientEncryption object to access the following explicit encryption methods:


Enable Client-Side Field Level Encryption on Database Connection

The mongo client-side field level encrytion methods require a database connection with client-side field level encryption enabled. If the current database connection was not initiated with client-side field level encryption enabled, either:

  • Use the Mongo() constructor from the mongo shell to establish a connection with the required client-side field level encryption options. The Mongo() method supports both Amazon Web Services and Local Key Management Service (KMS) providers for Customer Master Key (CMK) management.


  • Use the mongo shell command line options to establish a connection with the required options. The command line options only support the AWS KMS provider for CMK management.


The getKeyVault() method automatically creates a unique index on the keyAltNames field with a partial index filter for only documents where keyAltNames exists. getKeyVault() creates this index in the key vault collection. This prevents any two data keys in the same key vault from having the same key alternative name and therefore avoids ambiguity around which data key is appropriate for encryption/decryption.


Do not drop the unique index created by getKeyVault(). Client-side field level encryption operations depend on server-enforced uniqueness of keyAltNames. Removing the index may lead to unexpected or unpredictable behavior.

The following example uses a locally managed KMS for the client-side field level encryption configuration.

Configuring client-side field level encryption for a locally managed key requires specifying a base64-encoded 96-byte string with no line breaks. The following operation generates a key that meets the stated requirements:

echo "$(head -c 96 /dev/urandom | base64 | tr -d '\n')"

Create a mongo shell session using the --nodb option and issue the following operation from that shell:

mongo --nodb

From the mongo shell session, issue the following operation to create the client-side field level encryption configuration object. Replace the key string with a valid base64-encoded 96-byte string, such as the one genereated using the code provided at the beginning of this example:

var ClientSideFieldLevelEncryptionOptions = {
  "keyVaultNamespace" : "encryption.__dataKeys",
  "kmsProviders" : {
    "local" : {
      "key" : BinData(0, "96-BYTE_LOCAL_KEY_STRING")

Use the Mongo() constructor to create a database connection with the client-side field level encryption options. Replace the mongodb:// URI with the connection string URI of the target cluster.

encryptedClient = Mongo(

Use the getClientEncryption() method to retrieve the client encryption object:

clientEncryption = encryptedClient.getClientEncryption()

For complete documentation on initiating MongoDB connections with client-side field level encryption enabled, see Mongo().