Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 6097B483 for ; Wed, 24 Aug 2016 13:27:11 +0000 (UTC) X-Greylist: delayed 00:28:34 by SQLgrey-1.7.6 Received: from slow1-d.mail.gandi.net (slow1-d.mail.gandi.net [217.70.178.86]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 7230E1E2 for ; Wed, 24 Aug 2016 13:27:10 +0000 (UTC) Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by slow1-d.mail.gandi.net (Postfix) with ESMTP id 3D87747BD5D for ; Wed, 24 Aug 2016 14:52:09 +0200 (CEST) Received: from mfilter22-d.gandi.net (mfilter22-d.gandi.net [217.70.178.150]) by relay6-d.mail.gandi.net (Postfix) with ESMTP id AF5F5FB8B8 for ; Wed, 24 Aug 2016 14:52:04 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mfilter22-d.gandi.net Received: from relay6-d.mail.gandi.net ([IPv6:::ffff:217.70.183.198]) by mfilter22-d.gandi.net (mfilter22-d.gandi.net [::ffff:10.0.15.180]) (amavisd-new, port 10024) with ESMTP id CcPF0GKlmbID for ; Wed, 24 Aug 2016 14:51:33 +0200 (CEST) X-Originating-IP: 178.19.221.38 Received: from [10.10.42.121] (unknown [178.19.221.38]) (Authenticated sender: thomasv@electrum.org) by relay6-d.mail.gandi.net (Postfix) with ESMTPSA id DFA66FB8EA for ; Wed, 24 Aug 2016 14:51:32 +0200 (CEST) To: bitcoin-dev@lists.linuxfoundation.org References: <201608232012.12588.luke@dashjr.org> From: Thomas Voegtlin Message-ID: <90bf12f2-e109-28b4-e93e-54bbc8002cb4@electrum.org> Date: Wed, 24 Aug 2016 14:51:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <201608232012.12588.luke@dashjr.org> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="agOisqevXgPn0K7qngdoRAkVcGpeQMFtB" X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] BIP Status updates (including to Active/Final Status) - BIP 39, BIP 43, BIP 44, BIP 67, BIP 111, BIP 125, BIP 130 X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Aug 2016 13:27:11 -0000 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --agOisqevXgPn0K7qngdoRAkVcGpeQMFtB Content-Type: multipart/mixed; boundary="0dptqkpxmdk7p9erhnHGA25XE1EmQMBvJ" From: Thomas Voegtlin To: bitcoin-dev@lists.linuxfoundation.org Message-ID: <90bf12f2-e109-28b4-e93e-54bbc8002cb4@electrum.org> Subject: Re: [bitcoin-dev] BIP Status updates (including to Active/Final Status) - BIP 39, BIP 43, BIP 44, BIP 67, BIP 111, BIP 125, BIP 130 References: <201608232012.12588.luke@dashjr.org> In-Reply-To: <201608232012.12588.luke@dashjr.org> --0dptqkpxmdk7p9erhnHGA25XE1EmQMBvJ Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Le 23/08/2016 =E0 22:12, Luke Dashjr via bitcoin-dev a =E9crit : > BIP 39: Mnemonic code for generating deterministic keys > - Used by many wallets and hundreds of thousands of users. >=20 > BIP 44: Multi-Account Hierarchy for Deterministic Wallets > - Appears to be implemented by multiple wallets. >=20 I personally believe that BIP39/BIP44 is a bad design. There is limited support for these BIPs in Electrum, in order to provide compatibility with hardware wallets. However, I do not plan to use BIP39/BIP44 for default Electrum wallets, for the following reasons. (Note that it does not make sense to consider BIP39 and BIP44 independently. Any wallet that decides to implement one without the other would be considered as broken.) Here is why I rejected this design: 1 - BIP44 uses multiple accounts. This means that in order to be compatible with the standard, a wallet *must* implement multiple accounts. A wallet that decides to keep things simple and use only one account, will not allow users to recover all their funds when they restore from a BIP39 seed, and will be considered as broken. 2 - An appealing feature of deterministic wallets is that you can use the same instance of your wallet on different devices. Two instances of your wallet can automatically synchronize their Bitcoin addresses, and display the same balance. The problem is that hardened derivations break this property. Indeed, with hardened derivations, software wallets need to ask the user's password in order to derive new accounts. Therefore, in order to implement automated detection of newly created accounts, a BIP44-compatible software wallets would need to ask the user's password whenever a new account is detected. This means that the wallet would ask the password without the user initiating any action. This seems to be an avenue for malware. Of course, hardware wallets do not have that issue, because they can derive new accounts without requesting a password from the user. BIP44 is a standard that has been designed for hardware wallets, but that makes things really difficult for software wallets. 3 - Unneeded complexity. From an end user perspective, the multiple accounts in BIP44 achieve the same result as using different derivation passphrases with the same BIP39 seed phrase. The only real difference is that BIP44 accounts can be enumerated deterministically, while passphrases in general cannot. However, this property is of limited interest, because automatic synchronization of multiple accounts cannot be guaranteed for bip44 software wallets, as explained in 2. 4 - BIP39 is inconsistent. It uses a hash of the utf8 encoded 'seed phrase' in order to derive the BIP32 seed. This hash-based derivation was added on my suggestion, in order to make the BIP independent from the particular wordlist used to generate the seed phrases. However, BIP39 also requires the implementation of a checksum, in order to verify that a seed phrase is valid. Suprisingly, the specification of the checksum involves wordlist indices. This means the checksum (and thus the BIP) requires a fixed wordlist. This defeats the purpose of using a hash for the derivation of the seed. The authors of the BIP should either have used hash functions for both the seed AND the checksum (that is what Electrum does), or for none of them (in that case case, you can have a bidirectional function between seed phrases and entropy, which is nice if you want to perform Shamir secret sharing of seed phrases, at the expenses of a fixed wordlist). In its current state, BIP39 takes the worst of both worlds. 5 - The fact that the wordlist must be part of BIP39, and cannot be changed in the future, seems a terrible idea to me. I believe that a specification should always try to be minimal. In that case, the specification includes a 2000+ words dictionary, when it could have avoided that. Even if you decide that BIP39 is final, there will always be users requiring the addition of wordlists for new languages. So, in practice, this BIP will never be final. 6 - Finally, and most importantly, BIP39 seed phrases do not have a version number. Without a version number, how are you going to derive addresses from a BIP39 seed phrase, when wallets start to use to new derivation methods (such as SegWit, or Schnorr signatures)? Does it mean that a BIP39 compatible wallet will have to check addresses from all the derivation methods that ever existed in the past, in order to ensure that all coins are correctly retrieved? Or will there be users that cannot access their coins because their BIP39 seed phrase is too old for newer software? --0dptqkpxmdk7p9erhnHGA25XE1EmQMBvJ-- --agOisqevXgPn0K7qngdoRAkVcGpeQMFtB Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBCgAGBQJXvZhUAAoJECvVgkt/lHDmVtwQAIHC/3w70S8N7wj5vpMqlcle zppgR+OTZFwndOOBg5NB+S9xaKVT7QHA/8WswFP0i5bJsIUafLHEkTwsQUVHk6fr elcbYNu5KenNnIKDQUNAVGH/nCdlrI0uZAko5fSyW5FuhNkj90cZ+N8AzYQW/PIr 4KJOlSqq9NS4YVDLBha5Kv2d2qCN5RJ/kdhhhlYDfVo/MIMKguiY7J1UyBb3X7nJ w0wZNl3oM6exzo80qBNRwtis6OiaSbUFOst6tbcH+uWM/Kw7ByEeNtfoUQgaKead MQGgQfgdLj+w8lY0Dl/lyjDMAJOpN69wh4N3DPi9g1N4GZxZpEQGikRpBbAoFblP LXELC9/FSxm+z1hG36Xbh7zuqDv75ViU9ZcOVuUEys5S7bx1tC5I5sh0aJz/HGr+ REdKclsDReJK9FPbPyrZil5mAJk4PW4542AOTfWwcu/s7x/GeiDQpC8b98rafs82 Xie6H9P6qgjO6TkXSawK9ZuztnabNUgfXnLOth6kXYlZ1A7g3reNte1J0C2tGe3w VthAEuhmOYaRNsfgG8Cj07Xxzdy1toLnf5gKG2tdLpxwdTd2EkWauxakWwx3ZYvF lDF0P8AC33vab0N0YMFeFf1bvd8cYRGEDjDX2+aiFr5pWfB1mDPH/G3tEFZ3vUKv XADa85HwdC+jtB49RMgE =3db2 -----END PGP SIGNATURE----- --agOisqevXgPn0K7qngdoRAkVcGpeQMFtB--