New constructs an encryption interface (the modified blockcipher) with a base key derived from a shared secret (using a private key and the counterparty's public key) hashed with a salt.

NewDecrypter constructs an el-Gamal decrypter the receiving party uses the public key must be the ephemeral return value of the Encrypter constructor.

NewEncryptor constructs an El-Gamal encryptor this involves generating an ephemeral key pair the public part of which is returned as it is needed for the counterparty to decrypt.