class ActiveSupport::MessageEncryptor

crypt.decrypt_and_verify(encrypted_data) # => “my secret data”
encrypted_data = crypt.encrypt_and_sign(‘my secret data’) # => “NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh…”
crypt = ActiveSupport::MessageEncryptor.new(key) # => #<ActiveSupport::MessageEncryptor …>
key = ActiveSupport::KeyGenerator.new(‘password’).generate_key(salt, 32) # => “x89xE0x156xAC…”
salt = SecureRandom.random_bytes(64)
where you don’t want users to be able to determine the value of the payload.
This can be used in situations similar to the MessageVerifier, but
to you.
The cipher text and initialization vector are base64 encoded and returned
somewhere you don’t trust.
MessageEncryptor is a simple way to encrypt values which get stored

def self.key_len(cipher = DEFAULT_CIPHER)

Given a cipher, returns the key length of the cipher to help generate the key of desired size 
def self.key_len(cipher = DEFAULT_CIPHER)
  OpenSSL::Cipher.new(cipher).key_len
end

def _decrypt(encrypted_message) 

def _decrypt(encrypted_message)
  cipher = new_cipher
  encrypted_data, iv = encrypted_message.split("--".freeze).map {|v| ::Base64.strict_decode64(v)}
  cipher.decrypt
  cipher.key = @secret
  cipher.iv  = iv
  decrypted_data = cipher.update(encrypted_data)
  decrypted_data << cipher.final
  @serializer.load(decrypted_data)
rescue OpenSSLCipherError, TypeError, ArgumentError
  raise InvalidMessage
end

def _encrypt(value) 

def _encrypt(value)
  cipher = new_cipher
  cipher.encrypt
  cipher.key = @secret
  # Rely on OpenSSL for the initialization vector
  iv = cipher.random_iv
  encrypted_data = cipher.update(@serializer.dump(value))
  encrypted_data << cipher.final
  "#{::Base64.strict_encode64 encrypted_data}--#{::Base64.strict_encode64 iv}"
end

def decrypt_and_verify(value)

avoid padding attacks. Reference: http://www.limited-entropy.com/padding-oracle-attacks.
Decrypt and verify a message. We need to verify the message in order to 
def decrypt_and_verify(value)
  _decrypt(verifier.verify(value))
end

def encrypt_and_sign(value)

padding attacks. Reference: http://www.limited-entropy.com/padding-oracle-attacks.
Encrypt and sign a message. We need to sign the message in order to avoid 
def encrypt_and_sign(value)
  verifier.generate(_encrypt(value))
end

def initialize(secret, *signature_key_or_options)

* :serializer - Object serializer to use. Default is +Marshal+.
* :digest - String of digest to use for signing. Default is +SHA1+.
OpenSSL::Cipher.ciphers. Default is 'aes-256-cbc'.
* :cipher - Cipher to use. Can be any cipher returned by
Options:

derivation function.
key by using ActiveSupport::KeyGenerator or a similar key
bits. If you are using a user-entered secret, you can generate a suitable
the cipher key size. For the default 'aes-256-cbc' cipher, this is 256
Initialize a new MessageEncryptor. +secret+ must be at least as long as 
def initialize(secret, *signature_key_or_options)
  options = signature_key_or_options.extract_options!
  sign_secret = signature_key_or_options.first
  @secret = secret
  @sign_secret = sign_secret
  @cipher = options[:cipher] || 'aes-256-cbc'
  @verifier = MessageVerifier.new(@sign_secret || @secret, digest: options[:digest] || 'SHA1', serializer: NullSerializer)
  @serializer = options[:serializer] || Marshal
end

def new_cipher 

def new_cipher
  OpenSSL::Cipher.new(@cipher)
end

def verifier 

def verifier
  @verifier
end