Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1W4fKG-0008BC-6L for bitcoin-development@lists.sourceforge.net; Sat, 18 Jan 2014 23:29:16 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of taplink.co designates 50.117.27.232 as permitted sender) client-ip=50.117.27.232; envelope-from=jeremy@taplink.co; helo=mail.taplink.co; Received: from mail.taplink.co ([50.117.27.232]) by sog-mx-1.v43.ch3.sourceforge.com with smtp (Exim 4.76) id 1W4fKF-0003BF-1A for bitcoin-development@lists.sourceforge.net; Sat, 18 Jan 2014 23:29:15 +0000 Received: from [10.115.119.149] ([166.147.71.166]) by mail.taplink.co ; Sat, 18 Jan 2014 15:24:10 -0800 References: <20140114225321.GT38964@giles.gnomon.org.uk> <20140116212805.GA4421@petertodd.org> <20140117144601.GA8614@petertodd.org> <52DA093D.4070505@gmail.com> Mime-Version: 1.0 (1.0) In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Message-Id: <52F8B4EC-F955-46E4-B871-3BEEFF69907D@taplink.co> X-Mailer: iPhone Mail (10B146) From: Jeremy Spilman Date: Sat, 18 Jan 2014 17:12:58 -0600 To: Gregory Maxwell oclient: 166.147.71.166#jeremy@taplink.co#465 X-Spam-Score: -2.0 (--) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record -0.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1W4fKF-0003BF-1A Cc: Bitcoin Development Subject: Re: [Bitcoin-development] Stealth Addresses X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Jan 2014 23:29:16 -0000 > On Fri, Jan 17, 2014 at 8:55 PM, Alan Reiner wrote: >> Isn't there a much faster asymmetric scheme that we can use? I've heard p= eople talk about ed25519, though I'm not sure it can be used for encryption.= >=20 > Doing ECDH with our curve is within a factor of ~2 of the fastest > encryption available at this security level, AFAIK. And separate > encryption would ~double the amount of data vs using the ephemeral key > for derivation. >=20 > Using another cryptosystem would mandate carry around additional code > for a fast implementation of that cryptosystem, which wouldn't be > fantastic. >=20 > So I'm not sure much can be improved there. In the case where payment is being sent only to Q1, and Q2 is for discovery o= nly, perhaps we could use a 160-bit curve for d2/Q2 and e/P resulting in 20 b= yte vs 32 bytes in the OP_RETURN, and of course faster multiplication.=20 80-bits of security I assume still greatly exceeds the actual level of priva= cy you get with the overall solution, and since Q2 is never protecting actua= l funds... But if it's a "real weakening" of the privacy then definitely not worth it, a= nd even the added complexity of another curve seems possibly not worth it...=