pub async fn seal<C, M, P>( cipher: C, message: M, dest_pub_key: P ) -> Result<(), OneErr>where C: Into<BufWrite> + 'static + Send, M: Into<BufRead> + 'static + Send, P: Into<BufReadSized<sodoken::::crypto_box::curve25519xchacha20poly1305::seal::{constant#0}>> + 'static + Send,
seal (encrypt) a message with an ephemeral key that can’t even be decrypted by this sender.