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New in version 4.2.


ClientEncryption.decrypt() decrypts the encryptionValue if the current database connection was configured with access to the Key Management Service (KMS) and key vault used to encrypt encryptionValue.

Returns:The decrypted value.

ClientEncryption.decrypt has the following syntax:

clientEncryption = db.getMongo().getClientEncryption()

The encryptedValue must be a binary data object with subtype 6 created using client-side field level encryption.

Read operations issued from a database connection configured with access to the correct Key Management Service (KMS) and Key Vault can automatically decrypt field values encrypted using ClientEncryption.encrypt(). Clients only need to use decrypt() to decrypt Binary subtype 6 values not stored within a document field.

The mongosh client-side field level encryption 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:

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


Start the mongosh client.

mongosh --nodb

To configure client-side field level encryption for a locally managed key, generate a base64-encoded 96-byte string with no line breaks.

const TEST_LOCAL_KEY = require("crypto").randomBytes(96).toString("base64")

Create the client-side field level encryption options using the generated local key string:

var autoEncryptionOpts = {
"keyVaultNamespace" : "encryption.__dataKeys",
"kmsProviders" : {
"local" : {
"key" : BinData(0, TEST_LOCAL_KEY)

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

encryptedClient = Mongo(

Retrieve the ClientEncryption object and use the ClientEncryption.decrypt() method to decrypt a value encrypted by ClientEncryption.encrypt().

clientEncryption = encryptedClient.getClientEncryption();

If successful, decrypt() returns the decrypted value:


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

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