symmetric encryption

Symmetric Encryption for Ruby Projects using OpenSSL


Symmetric Encryption

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Transparently encrypt ActiveRecord, and Mongoid attributes. Encrypt passwords in configuration files. Encrypt entire files at rest.


Any project that wants to meet PCI compliance has to ensure that the data is encrypted
whilst in flight and at rest. Amongst many other requirements all passwords
in configuration files also have to be encrypted.

Symmetric Encryption helps achieve compliance by supporting encryption of data in a simple
and consistent way.

Symmetric Encryption uses OpenSSL to encrypt and decrypt data, and can therefore
expose all the encryption algorithms supported by OpenSSL.


Symmetric Encryption Guide

Rocket Job

Checkout the sister project Rocket Job: Ruby’s missing batch system.

Fully supports Symmetric Encryption to encrypt data in flight and at rest while running jobs in the background.

Upgrading to Rails V7

There is a method naming conflict with Rails 7, which has its own encrypted_attributes method.

As a result the older attr_encrypted mechanism is no longer available with Rails 7.
Migrate the use of attr_encrypted to attribute as described in the Frameworks Guide.

Upgrading to SymmetricEncryption V4

Version 4 of Symmetric Encryption has completely adopted the Ruby keyword arguments on most API’s where
multiple arguments are being passed, or where a Hash was being used before.

The encrypt and decrypt API now require keyword arguments for any optional arguments.

The following does not change:

encrypted = SymmetricEncryption.encrypt('Hello World')

The following is not backward compatible:

SymmetricEncryption.encrypt('Hello World', false, false, :date)

Needs to be changed to:

SymmetricEncryption.encrypt('Hello World', random_iv: false, compress: false, type: :date)

Or, just to change the type:

SymmetricEncryption.encrypt('Hello World', type: :date)

Similarly the decrypt api has also changed:

SymmetricEncryption.decrypt(encrypted, 2, :date)

Needs to be changed to:

SymmetricEncryption.decrypt(encrypted, version: 2, type: :string)

The Rake tasks have been replaced with a new command line interface for managing key configuration and generation.
For more info:

symmetric-encryption --help

Configuration changes

In Symmetric Encryption V4 the configuration file is now modified directly instead
of using templates. This change is necessary to allow the command line interface to
generate new keys and automatically update the configuration file.

Please backup your existing symmetric-encryption.yml prior to upgrading if it is not
already in a version control system. This is critical for configurations that have custom
code or for prior configurations targeting heroku.

In Symmetric Encryption V4 the defaults for encoding and always_add_header have changed.
If these values are not explicitly set in the symmetric-encryption.yml file, set them
prior to upgrading.

Prior defaults, set explicitly to these values if missing for all environments:

      encoding:          :base64
      always_add_header: false

New defaults are:

      encoding:          :base64strict
      always_add_header: true

Upgrading to SymmetricEncryption V3

In version 3 of SymmetricEncryption, the following changes have been made that
may have backward compatibility issues:

  • SymmetricEncryption.decrypt no longer rotates through all the decryption keys
    when previous ciphers fail to decrypt the encrypted string.
    In a very small, yet significant number of cases it was possible to decrypt data
    using the incorrect key. Clearly the data returned was garbage, but it still
    returned a string of data instead of throwing an exception.
    See SymmetricEncryption.select_cipher to supply your own custom logic to
    determine the correct cipher to use when the encrypted string does not have a
    header and multiple ciphers are defined.

  • Configuration file format prior to V1 is no longer supported.

  • New configuration option has been added to support setting encryption keys
    from environment variables.

  • Cipher.parse_magic_header! now returns a Struct instead of an Array.

  • New config options :encrypted_key and :encrypted_iv to support setting
    the encryption key in environment variables, or from other sources such as ldap
    or a central directory service.

New features in V1.1 and V2

  • Ability to randomly generate a new initialization vector (iv) with every
    encryption and put the iv in the encrypted data as its header, without having
    to use SymmetricEncryption::Writer.

  • With file encryption randomly generate a new key and initialization vector (iv) with every
    file encryption and put the key and iv in the encrypted data as its header which
    is encrypted using the global key and iv.

  • Support for compression.

  • SymmetricEncryption.encrypt has two additional optional parameters:

    • random_iv [true|false]

      • Whether the encypted value should use a random IV every time the
        field is encrypted.
      • It is recommended to set this to true where feasible. If the encrypted
        value could be used as part of a SQL where clause, or as part
        of any lookup, then it must be false.
      • Setting random_iv to true will result in a different encrypted output for
        the same input string.
      • Note: Only set to true if the field will never be used as part of
        the where clause in an SQL query.
      • Note: When random_iv is true it will add a 8 byte header, plus the bytes
        to store the random IV in every returned encrypted string, prior to the
        encoding if any.
      • Note: Adds a 6 byte header prior to encoding, if not already configured
        to add the header to all encrypted values.
      • Default: false
      • Highly Recommended where feasible: true
    • compress [true|false]

      • Whether to compress prior to encryption.
      • Should only be used for large strings since compression overhead and
        the overhead of adding the ‘magic’ header may exceed any benefits of
      • Default: false


Reid Morrison



This project uses Semantic Versioning.


Although this library has assisted in meeting PCI Compliance and has passed
previous PCI audits, it in no way guarantees that PCI Compliance will be
achieved by anyone using this library.