Crypt::DES_EDE3 implements DES-EDE3 encryption. This is triple-DES encryption where an encrypt operation is encrypt-decrypt-encrypt, and decrypt is decrypt-encrypt-decrypt. This implementation uses Crypt::DES to do its dirty DES work, and simply provides a wrapper around that module: setting up the individual DES ciphers, initializing the keys, and performing the encryption/decryption steps. DES-EDE3 encryption requires a key size of 24 bytes.