From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WJj3I-0005Kl-32 for bitcoin-development@lists.sourceforge.net; Sat, 01 Mar 2014 12:30:00 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.220.47 as permitted sender) client-ip=209.85.220.47; envelope-from=elombrozo@gmail.com; helo=mail-pa0-f47.google.com; Received: from mail-pa0-f47.google.com ([209.85.220.47]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WJj3H-00056G-4G for bitcoin-development@lists.sourceforge.net; Sat, 01 Mar 2014 12:30:00 +0000 Received: by mail-pa0-f47.google.com with SMTP id lj1so1925774pab.20 for ; Sat, 01 Mar 2014 04:29:53 -0800 (PST) X-Received: by 10.66.182.199 with SMTP id eg7mr9225463pac.135.1393676993276; Sat, 01 Mar 2014 04:29:53 -0800 (PST) Received: from [192.168.1.107] (cpe-76-88-33-166.san.res.rr.com. [76.88.33.166]) by mx.google.com with ESMTPSA id sm5sm2025056pab.19.2014.03.01.04.29.50 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 01 Mar 2014 04:29:51 -0800 (PST) From: Eric Lombrozo Content-Type: multipart/signed; boundary="Apple-Mail=_449E2016-C8B9-49D1-B3D2-D63D90C89667"; protocol="application/pgp-signature"; micalg=pgp-sha1 Message-Id: Date: Sat, 1 Mar 2014 04:29:48 -0800 To: bitcoin-development@lists.sourceforge.net Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) X-Mailer: Apple Mail (2.1510) 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 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (elombrozo[at]gmail.com) -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: 1WJj3H-00056G-4G Subject: [Bitcoin-development] Making the H in HD keychains useful 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, 01 Mar 2014 12:30:00 -0000 --Apple-Mail=_449E2016-C8B9-49D1-B3D2-D63D90C89667 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii I've been trying to find ways to make HD keychain wallets (BIP0032) = really usable from an application development perspective. I think we = all know a number of solid use cases and possible applications for the D = in HD, but nobody seems to have really found a way to make use of the H = in a way that is actually manageable from a usability standpoint. After pondering it a bit more, I think I've stumbled upon at least a = couple issues that seem to give hints as to how we can change this. Hierarchical organizations do not generally tend to be designed up = front, cast in stone. In the real world, hierarchies tend to evolve = organically, growing new branches as entities differentiate themselves = to different purposes. Organizations grow over time. Sometimes branches = merge, sometimes branches die. This means that for HD keychains to be = truly useful, they too need to be sufficiently flexible to adapt to the = needs of a growing and evolving organization. It needs to be simple to = create and move branches around as the need for them arises without = having to plan the structure a priori. A significant problem I'm runnign into in trying to build applications = around the BIP0032 standard is the lack of a clear separation between = signing keys and hierarchical nodes. That's to say, a child of a node = can either be used as a signing key or as a parent for new branches to = the tree. =46rom a usability standpoint, what this means is that one = must be very careful in how one allocates keys from the very beginning - = if one mixes signing keys with new branching nodes in the same = generation, the whole thing becomes a horrendous mess. Moreover, it is = impossible to generally distinguish these two fundamentally different = types of objects (at least from a use model perspective) just from the = extended key representation, something that is certain to create = significant confusion as we try to design applications that can share = these types of objects. An organization might begin as a single individual who just wants to = generate signing keys for him/herself. Later on, this individual might = bring on another individual or two and create new branches for them. = With the current HD keychain structure, unless this individual made sure = to set aside these new branches from the start, the individual is now = forced to mix the new branches in at the same level of the hierarchy as = the signing keys. Instead, it should be possible to branch off any node = without having to worry at all about whether or not that node has been = used to generate signing keys at all. A possible workaround to this issue is to always allocate a specific = child for hierarchical derivation and the rest of the children for = signing keys. Then to create subbranches, the specific child would be = used as the new parent, effectively alternating generations between = signing keys and organizational nodes. However, this solution seems = pretty ugly. A better solution, IMO, is to only use BIP0032 for organizational = hierarchy and have a different mechanism for generating a sequence of = signing keys from a given node. This different mechanism could be used = standalone by those not needing the full set of hierarchical features. = For those who do want to use the hierarchical features, it could be = seeded by the keys in the BIP0032 hierarchy. These individual signing = keys would NEVER be represented in the same format as the organizational = hierarchy nodes, thus ensuring applications can share these structures = without risk of confusion. Until we make this clear distinction between organizational hierarchy = (which parallels real-world organizations) and signing keys (which are = merely cryptographic primitives, preferably never even shown directly to = most endusers), I think we'll fail to find good ways to make the H in HD = keychains useful. -Eric Lombrozo --Apple-Mail=_449E2016-C8B9-49D1-B3D2-D63D90C89667 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- iQIcBAEBAgAGBQJTEdK8AAoJEAA1EyJsW9n+mDcP/jcJqZ/Z3vbOzACBUJa3Kc2g YjRJUD4TTXL7xrDpenVpmFQF5XVCCNTzt7aYo1Un1WZlGbeoIw2hzuaE4upU0bfT RVcBr71+iSlU3E2SubY7LS8TXDd28GGoeb73HYlq44xLcuuOITLljkQjE21fg6dq kh/rlBY31B0be0H1btESfG0ekzx2v0mvOs+dWefANX2MoGJpJtL0ZUyUmBRxYgdk lEcxYXsP53CpMdcikR3EX1LjnWHqDaR/6dLhCnV3Ko6mZAFyXuK3Udj/FtskKlDG RbquFY6z/ZzdAJSrOo8iUVGMyQdEektlNunHt7hyXmwwD7Hjn1KkWSlPQd3h3bcs WE1BGcL9lVrXnmBTkfGm9KMgyiYHu63hr85cZ44vg3QIVTXUOzXnzYFVulgfDM6v mZLSFIaVdCXx6bKX/oFedx1Z/vKtmazNXoga2bG53YDLGHay+06fydDykQ7mlSe9 mtxV7cIf3F7MXlVyFeHSPnH/5eY98iH3jFc5B+QTyk+0IAN61GJ/tvXcR6tggg6+ kYwY+HBVz2LUKAYrJVvqB5noAazP9V+no/VEHA+K3jWPvBP+9AlSr1AfO0yeT4k2 gWQ7INCSn1QWX0/h+NiKbVRz/uYWQEWaSIdscKmuZK97dhRkaUGfGy01xdErQUX6 vcu8zpRgdXYdT51O18rw =glfk -----END PGP SIGNATURE----- --Apple-Mail=_449E2016-C8B9-49D1-B3D2-D63D90C89667--