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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



To mitigate the risk of the AWS Access Key or AWS Secret Key leaking into logs, consider specifying an environment variable containing the required values as part of the mongo startup. For example, the following operation loads the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables into local variables in the mongo shell:

mongo --eval "
  " \

Use the created AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY variables in the shell to reference the AWS credentials.

The following operation issued from the mongo shell:

  • Establishes a connection to the cluster with client-side field level encryption enabled.
  • Retrieves the ClientEncryption object using the getClientEncryption() constructor on an encryption-enabled connection.
  • Explicitly encrypts a value using random encryption.
clientSideFLEOptions = {
  "keyVaultNamespace" : "encryption.dataKeys",
  "kmsProviders" : {
    "aws" : {
      "accessKeyId" : "AWS_ACCESS_KEY_ID",
      "secretAccessKey" : "AWS_SECRET_ACCESS_KEY"

encryptedClient = Mongo(

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().