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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.

ClientEncryption.encrypt(encryptionKeyId, value, encryptionAlgorithm)

ClientEncryption.encrypt encrypts the value using the specified encryptionKeyId and encryptionAlgorithm. encrypt supports explicit (manual) encryption of field values.

encrypt has the following syntax:

clientEncryption = db.getMongo().getClientEncryption()

Parameter Type Description
encryptionKeyId UUID

The data key to use for encrypting the value.

The UUID is a BSON binary data object with subtype 4 that identifies a specific data key. If the data key does not exist in the key vault configured for the database connection, encrypt() returns an error.

value See Unsupported BSON Types. The value to encrypt.
encryptionAlgorithm string

The encryption algorithm to use for encrypting the value.

  • AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic
  • AEAD_AES_256_CBC_HMAC_SHA_512-Random

For complete documentation on the supported encryption algorithms, see Encryption Algorithms.

returns:A binary data object with subtype 6.


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.

Unsupported BSON Types

encrypt() does not supports encrypting values with the following BSON types:

  • minKey
  • maxKey
  • null
  • undefined

If encrypting a field using AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic, encrypt() does not support the following BSON types:

  • double
  • decimal128
  • bool
  • object
  • array
  • javascriptWithScope


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(

Retrieve the ClientEncryption object and use the ClientEncryption.encrypt() method to encrypt a value using a specific data key UUID and encryption algorithm:

clientEncryption = encryptedClient.getClientEncryption();


If sucessful, encrypt returns the encrypted value:


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