Reversible encryption in RoR

reversible_encrypted_attribute.rb

# frozen_string_literal: true

# Use Active Record Encryption for newer version of Rails
# https://edgeguides.rubyonrails.org/active_record_encryption.html
module ReversibleEncryptedAttribute
  extend ActiveSupport::Concern

  COLUMN_PREFIX = "encrypted"

  class_methods do
    # @param key [Symbol,String]
    def encrypted_attribute(key)
      column_name = "#{COLUMN_PREFIX}_#{key}"

      # @param value [String,nil]
      define_method "#{key}=" do |value|
        public_send("#{column_name}=", encrypt(value))
      end

      # @return [String,nil]
      define_method key do
        return unless public_send("#{column_name}?")

        decrypt(public_send(column_name))
      end
    end
  end

  private

  def encryptor
    @encryptor ||= ActiveSupport::MessageEncryptor.new(encryption_key)
  end

  def encrypt(value)
    return if value.blank?

    encryptor.encrypt_and_sign(value)
  end

  def decrypt(encrypted)
    encryptor.decrypt_and_verify(encrypted)
  end

  # Must be 32 bytes
  def encryption_key
    raise "#{__method__} should be implemented."
  end
end