Quote from: YarkoL on June 10, 2015, 08:19:10 PM

i.e by what procedure do you replace the ephem keypair with
just one number?

Well the ephem keypair is only required for traditional stealth payments because that's how both parties can calculate the shared secret. That's not necessary in my first scenario because only the public address of the payee is required to encrypt the randomly generated shared secret. It's probably easier to think about my second scenario, the one I gave in the edit. In that scenario the ephem keypair is still required to calculate the first shared secret like normal, but we use it as the key for a symmetric encryption algorithm so that we can encrypt the randomly generated shared secret. The second random shared secret is what we actually use to calculate Q'.

Quote from: YarkoL on June 10, 2015, 08:19:10 PM

I think you mean the payer multiplies his private key with the public key
of the payee? He can't have the private key of the other party.

Yes that is what I meant, I have corrected it now.