Function encrypt_and_mac 

fn encrypt_and_mac(
    plaintext: &[u8],
    other_data: &[u8],
    public_key: &PublicKey,
    enc_key: &Zeroizing<[u8; 32]>,
    mac_key: [u8; 32],
) -> (Vec<u8>, CtByteArray<HS_MAC_LEN>)

Encrypt the ‘plaintext’ using ‘enc_key’. Then compute the intro cell MAC using ‘mac_key’ over the text (other_text, public_key, plaintext) and return (ciphertext, mac_tag).