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2.1.3 • Public • Published


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A simple symmetric encryption plugin for individual fields. The goal of this plugin is to encrypt data but still allow searching over fields with string values. This plugin relies on the Node crypto module. Encryption and decryption happen transparently during save and find.

As of the stable 1.0.0 release, this plugin works on individual fields of any type. However, note that for non-string fields, the original value is set to undefined after encryption. This is because if the schema has defined a field as an array, it would not be possible to replace it with a string value.

Also consider mongoose-encryption if you are looking to encrypt the entire document.

How it works

Encryption is performed using AES-256-CBC. To encrypt, the relevant fields are encrypted with the provided secret + random salt. The generated salt and the resulting encrypted value is concatenated together using a : character and the final string is put in place of the actual value for string values. An extra boolean field with the prefix __enc_ is added to the document which indicates if the provided field is encrypted or not.

Fields which are either objects or of a different type are converted to strings using JSON.stringify and the value stored in an extra marker field of type string with a naming scheme of __enc_ as prefix and _d as suffix on the original field name. The original field is then set to undefined. Please note that this might break any custom validation and application of this plugin on non-string fields needs to be done with care.


  • Node >=4.4.7
  • MongoDB >=2.6.10
  • Mongoose >=4.0.0


npm install mongoose-field-encryption

Security Notes

  • Always store your keys and secrets outside of version control and separate from your database. An environment variable on your application server works well for this.
  • Additionally, store your encryption key offline somewhere safe. If you lose it, there is no way to retrieve your encrypted data.
  • Encrypting passwords is no substitute for appropriately hashing them. bcrypt is one great option. You can also encrypt the password afer hashing it although it is not necessary.
  • If an attacker gains access to your application server, they likely have access to both the database and the key. At that point, neither encryption nor authentication do you any good.



For example, given a schema as follows:

const mongoose = require("mongoose");
const mongooseFieldEncryption = require("mongoose-field-encryption").fieldEncryption;
const Schema = mongoose.Schema;
const Post = new Schema({
  title: String,
  message: String,
  references: {
    author: String,
    date: Date
Post.plugin(mongooseFieldEncyption, { fields: ["message", "references"], secret: "some secret key" });

The resulting documents will have the following format:

  _id: ObjectId,
  title: String,
  message: String, // encrypted salt and hex value as string, e.g. 9d6a0ca4ac2c80fc84df0a06de36b548:cee57185fed78c055ed31ca6a8be9bf20d303283200a280d0f4fc8a92902e0c1
  __enc_message: true, // boolean marking if the field is encrypted or not
  references: undefined, // encrypted object set to undefined
  __enc_references: true, // boolean marking if the field is encrypted or not
  __enc_references_d: String // encrypted salt and hex object value as string, e.g. 6df2171f25fd1d32adc4a4059f867a82:5909152856cf9cdb7dc32c6af321c8fe69390c359c6b19d967eaa6e7a0a97216

find works transparently and you can make new documents as normal, but you should not use the lean option on a find if you want the fields of the document to be decrypted. findOne, findById and save also all work as normal. update works only for string fields and you would also need to manually set the __enc_ field value to false if you're updating an encrypted field.

From the mongoose package documentation: Note that findAndUpdate/Remove do not execute any hooks or validation before making the change in the database. If you need hooks and validation, first query for the document and then save it.

Note that as of 1.2.0 release, support for findOneAndUpdate has also been added. Note that you would need to specifically set the encryption field marker for it to be encrypted. For example:

Post.findOneAndUpdate({ _id: postId }, { $set: { message: "snoop", __enc_message: false } });

The above also works for non-string fields. See changelog for more details.

Also note that if you manually set the value __enc_ prefix field to true then the encryption is not run on the corresponding field and this may result in the plain value being stored in the db.


  • fields (required): an array list of the required fields
  • secret (required): a string cipher which is used to encrypt the data (don't lose this!)
  • useAes256Ctr (optional, default false): a boolean indicating whether the older aes-256-ctr algorithm should be used. Note that this is strictly a backwards compatibility feature and for new installations it is recommended to leave this at default.

Static methods

For performance reasons, once the document has been encrypted, it remains so. The following methods are thus added to the schema:

  • encryptFieldsSync(): synchronous call that encrypts all fields as given by the plugin options
  • decryptFieldsSync(): synchronous call that decrypts encrypted fields as given by the plugin options
  • stripEncryptionFieldMarkers(): synchronous call that removes the encryption field markers (useful for returning documents without letting the user know that something was encrypted)

Multiple calls to the above methods have no effect, i.e. once a field is encrypted and the __enc_ marker field value is set to true then the ecrypt operation is ignored. Same for the decrypt operation. Of course if the field markers have been removed via the stripEncryptionFieldMarkers() call, then the encryption will be executed if invoked.


To enable searching over the encrypted fields the encrypt and decrypt methods have also been exposed.

const fieldEncryption = require('mongoose-field-encryption')
const encrypted = fieldEncryption.encrypt('some text', 'secret'));
const decrypted = fieldEncryption.decrypt(encrypted, 'secret')); // decrypted = 'some text'


  1. Install dependencies with npm install and install mongo if you don't have it yet.
  2. Start mongo with mongod.
  3. Run tests with npm test. Additionally you can pass your own mongodb uri as an environment variable if you would like to test against your own database, for e.g. URI='mongodb://username:password@' npm test



release-it patch,minor,major


  • npm version patch,minor,major
  • npm publish



  • Fix bug where decryption fails when the field in question is not retrieved, PR #26.


  • Fix bug where data was not getting decrypted on a find(), #23.


  • Use cipheriv instead of plain cipher, #17.

    Note that this might break any fixed search capability as the encrypted values are now based on a random salt.

    Also note that while this version maintains backward compatibility, i.e. decryption will automatically fall back to using the aes-256-ctr algorithm, any further updates will lead to the value being encrypted with the salt. In order to fully maintain backwards compatibilty, an new option useAes256Ctr has been introduced (default false), which can be set to true to continue using the plugin as before. It is highly recommended to start using the newer algorithm however, see issue for more details.




npm i mongoose-field-encryption

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