elgamal.Decrypt
// Decrypt takes two integers, resulting from an ElGamal encryption, and
// returns the plaintext of the message. An error can result only if the
// ciphertext is invalid. Users should keep in mind that this is a padding
// oracle and thus, if exposed to an adaptive chosen ciphertext attack, can
// be used to break the cryptosystem. See “Chosen Ciphertext Attacks
// Against Protocols Based on the RSA Encryption Standard PKCS #1”, Daniel
// Bleichenbacher, Advances in Cryptology (Crypto '98),
func Decrypt(priv *PrivateKey, c1 *big.Int, c2 *big.Int) (msg []byte, err error)
elgamal.Encrypt
// Encrypt encrypts the given message to the given public key. The result is a
// pair of integers. Errors can result from reading random, or because msg is
// too large to be encrypted to the public key.
func Encrypt(random io.Reader, pub *PublicKey, msg []byte) (c1 *big.Int, c2 *big.Int, err error)