encrypt
AES256 encryption of arbitrary length messages. An initialization vector (IV) is generated and included with the ciphertext that is the cryptographic hash of the plaintext, the secret, and an incrementing value. The IV is included in the encrypted result so its size will be larger than the plaintext. For the maximum size efficiency when the IV can be inferred or calculated and the size is known use encryptAES256by16
Return
ciphertext or an empty array. The ciphertext length will be different than the plaintext since the IV is included.