From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WQweZ-00016i-67 for bitcoin-development@lists.sourceforge.net; Fri, 21 Mar 2014 10:26:19 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; envelope-from=gcbd-bitcoin-development@m.gmane.org; helo=plane.gmane.org; Received: from plane.gmane.org ([80.91.229.3]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1WQweX-0007UO-Ax for bitcoin-development@lists.sourceforge.net; Fri, 21 Mar 2014 10:26:19 +0000 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1WQweQ-0004e7-H8 for bitcoin-development@lists.sourceforge.net; Fri, 21 Mar 2014 11:26:10 +0100 Received: from e179064016.adsl.alicedsl.de ([85.179.64.16]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 21 Mar 2014 11:26:10 +0100 Received: from andreas by e179064016.adsl.alicedsl.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 21 Mar 2014 11:26:10 +0100 X-Injected-Via-Gmane: http://gmane.org/ To: bitcoin-development@lists.sourceforge.net From: Andreas Schildbach Date: Fri, 21 Mar 2014 11:25:59 +0100 Message-ID: References: <20140320121221.GA25052@netbook.cypherspace.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: e179064016.adsl.alicedsl.de User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 In-Reply-To: <20140320121221.GA25052@netbook.cypherspace.org> X-Enigmail-Version: 1.5.2 X-Spam-Score: -0.4 (/) 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 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [80.91.229.3 listed in list.dnswl.org] -0.0 SPF_HELO_PASS SPF: HELO matches SPF record 1.1 DKIM_ADSP_ALL No valid author signature, domain signs all mail -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1WQweX-0007UO-Ax Subject: Re: [Bitcoin-development] Payment Protocol for Face-to-face Payments 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: Fri, 21 Mar 2014 10:26:19 -0000 On 03/20/2014 01:12 PM, Adam Back wrote: > Whats a sensible limit on practical/convenient QR code size? Technically 3 KB. In my experience codes above 1.5 KB become impossible to scan (ZXing scanner, 3 years ago). You will want to stay below 500 bytes for convenient scanning. That said, I'm convinced there is a lot of room for scanning improvements. > How much of the payment protocol message size comes from use of x509? As said in the OP, a minimal PR uses 50 bytes. X.509 seems to put about 4000 bytes on top of that. As you can see, we have quite some room for improvements to PR payload (PaymentDetails). X.509 certification will probably not be possible via QR, at least not until specialized CA's will issue space-efficient certs (using ECDSA?).