Function seal_detached 

pub fn seal_detached(
    m: &mut [u8],
    n: &Nonce,
    pk: &PublicKey,
    sk: &SecretKey,
) -> Tag

seal_detached() encrypts and authenticates a message m using the senders secret key sk, the receivers public key pk and a nonce n. m is encrypted in place, so after this function returns it will contain the ciphertext. The detached authentication tag is returned by value.