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 1XSRdh-0004WU-8S for bitcoin-development@lists.sourceforge.net; Fri, 12 Sep 2014 14:15:53 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of bitpay.com designates 209.85.213.169 as permitted sender) client-ip=209.85.213.169; envelope-from=jgarzik@bitpay.com; helo=mail-ig0-f169.google.com; Received: from mail-ig0-f169.google.com ([209.85.213.169]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1XSRdb-0001X4-NN for bitcoin-development@lists.sourceforge.net; Fri, 12 Sep 2014 14:15:53 +0000 Received: by mail-ig0-f169.google.com with SMTP id a13so258451igq.2 for ; Fri, 12 Sep 2014 07:15:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-type; bh=ANToO82eeUD2UA4X/+wxgNyZtkF+Wunu7mEMd5XPdlI=; b=gknGyHXm6z9FmPC+a67NdMxUc0I5/LFPpnCVBW6mGo2XH0vsfeJzYpZJc6jK8JbTLN m84sBbC8ufeGeCmA3F7g1ea6lTDo2ecvDlY+3xYVM9roM34DAQJA2QjWkZTmxOJ7drDF i/bH2o3tl7c3lwyVJE+oLKLN46wvA2+M+oD2Nyhs5gVzwRqWct8XUGBRBLYigIjlNhHL YmPYAWV5d2Uz9BKj/ZtPJcbi5IFC4BOVKDMN5JtsesjR3xshzDR7zcz2Tg5QLryRS+3V HzgcqP+kx72ley+Ty0F72B/oehcdWAZWcXmXbZRN/qMjOgtoJtMSdPl20O23l53tydFm USqA== X-Gm-Message-State: ALoCoQmnrKgls7gKLh7CtMIehzzzoc6X4oKyJ3B+VTsfYt64/l0izyRLt6gXtZiCXZ6Eag5DbpJw X-Received: by 10.50.50.198 with SMTP id e6mr2594782igo.1.1410531342075; Fri, 12 Sep 2014 07:15:42 -0700 (PDT) MIME-Version: 1.0 Received: by 10.107.153.149 with HTTP; Fri, 12 Sep 2014 07:15:21 -0700 (PDT) In-Reply-To: References: From: Jeff Garzik Date: Fri, 12 Sep 2014 10:15:21 -0400 Message-ID: To: Mike Hearn Content-Type: text/plain; charset=UTF-8 X-Spam-Score: -1.6 (-) 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 -0.1 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: 1XSRdb-0001X4-NN Cc: Bitcoin Dev , Andreas Schildbach Subject: Re: [Bitcoin-development] BIP72 amendment proposal 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, 12 Sep 2014 14:15:53 -0000 Indeed -- Every byte added to the QR code makes it more difficult to be used in restaurants, pubs and other low-light conditions. BitPay tested some of these scenarios. Scannability is absolutely impacted. On Fri, Sep 12, 2014 at 9:49 AM, Mike Hearn wrote: > A few thoughts on this: > > (1) Base64 of SHA256 seems overkill. 256 bits of hash is a lot. The risk > here is that a MITM intercepts the payment request, which will be typically > requested just seconds after the QR code is vended. 80 bits of entropy would > still be a lot and take a long time to brute force, whilst keeping QR codes > more compact, which impacts scannability. > > (2) This should not be necessary in the common HTTPS context. The QR code > itself is going to be fetched from some service, over HTTPS. I see no > reasonable attacker that can MITM the request for the BIP70 message but not > the request to get the QR code. Adding a hash makes QR codes more bloated > and harder to scan, all on the assumption that HTTPS is broken in some odd > way that we haven't actually ever seen in practice. > > (3) This can be useful in the Bluetooth context, but then again, we could > also do things a different way by signing with the key in the first part of > the URI, thus avoiding the need for a hash. > > I know I've been around the loop on this one with Andreas many times. But > this BIP doesn't fix any actually existing problem in the previous spec. It > exists because Andreas thinks SSL is useless. If SSL is useless we all have > much bigger problems. > > ------------------------------------------------------------------------------ > Want excitement? > Manually upgrade your production database. > When you want reliability, choose Perforce > Perforce version control. Predictably reliable. > http://pubads.g.doubleclick.net/gampad/clk?id=157508191&iu=/4140/ostg.clktrk > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > -- Jeff Garzik Bitcoin core developer and open source evangelist BitPay, Inc. https://bitpay.com/