salt = SecureRandom.random_bytes(64)
key  = ActiveSupport::KeyGenerator.new('password').generate_key(salt) # => "\x89\xE0\x156\xAC..."
crypt = ActiveSupport::MessageEncryptor.new(key)            # => #<ActiveSupport::MessageEncryptor ...>
encrypted_data = crypt.encrypt_and_sign('my secret data')       # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
crypt.decrypt_and_verify(encrypted_data)                # => "my secret data"

class User < ActiveRecord::Base
 serialize :preferences, Hash
end

user = User.new
user.preferences = {
 gender: 'male',
 age: 18
}
user.save!

class CustomerSerializer
 def self.load(value)
  value.to_s.blank? ? "" : JSON.parse(value)
 end

 def self.dump(value)
  (value || {}).to_json
 end
end

class User < ActiveRecord::Base
 serialize :preferences, CustomerSerializer
end

class EncryptedStringSerializer
 def self.load(value)
  value.to_s.blank? ? '' : decrypt(value)
 end

 def self.dump(value)
  encrypt(value || '')
 end

 private

 def self.encrypt(value)
  encryptor.encrypt_and_sign(value)
 end

 def self.decrypt(value)
  encryptor.decrypt_and_verify(value)
 end

 def self.encryptor
  @encryptor ||= ActiveSupport::MessageEncryptor.new(Settings.message_encryptor_key)
 end
end

class UserAddress < ActiveRecord::Base
 serialize :phone, EncryptedStringSerializer
 serialize :first_name, EncryptedStringSerializer
 serialize :last_name, EncryptedStringSerializer
 serialize :country, EncryptedStringSerializer
 serialize :state, EncryptedStringSerializer
 serialize :city, EncryptedStringSerializer
 serialize :address1, EncryptedStringSerializer
 serialize :address2, EncryptedStringSerializer
 serialize :zipcode, EncryptedStringSerializer
end