On 21 April 2017 at 12:11, John Levine <johnl@xxxxxxxxx> wrote: > > If a recipient is cooperative, and sends you back a message signed > with the same key to which you encrypted the message, that tells you > he got it, but that's not a very interesting case. It's also abuse of the cryptographic primitives, I hope that this isn't really how it works and you are eliding certain key details.