Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WTwWR-0003YA-Le for bitcoin-development@lists.sourceforge.net; Sat, 29 Mar 2014 16:54:19 +0000 X-ACL-Warn: Received: from qmta09.westchester.pa.mail.comcast.net ([76.96.62.96]) by sog-mx-4.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1WTwWP-0003fl-4D for bitcoin-development@lists.sourceforge.net; Sat, 29 Mar 2014 16:54:19 +0000 Received: from omta19.westchester.pa.mail.comcast.net ([76.96.62.98]) by qmta09.westchester.pa.mail.comcast.net with comcast id jUnr1n00127AodY59UuBB4; Sat, 29 Mar 2014 16:54:11 +0000 Received: from crushinator.localnet ([IPv6:2601:6:4800:47f:219:d1ff:fe75:dc2f]) by omta19.westchester.pa.mail.comcast.net with comcast id jUuB1n0084VnV2P3fUuB7y; Sat, 29 Mar 2014 16:54:11 +0000 From: Matt Whitlock To: Tamas Blummer , bitcoin-development@lists.sourceforge.net Date: Sat, 29 Mar 2014 12:54:11 -0400 Message-ID: <4676777.MQU5AqByQt@crushinator> User-Agent: KMail/4.12.3 (Linux/3.12.13-gentoo; KDE/4.12.3; x86_64; ; ) In-Reply-To: References: <1878927.J1e3zZmtIP@crushinator> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Spam-Score: 0.0 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [76.96.62.96 listed in list.dnswl.org] 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: 1WTwWP-0003fl-4D Subject: Re: [Bitcoin-development] Presenting a BIP for Shamir's Secret Sharing of Bitcoin private keys 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, 29 Mar 2014 16:54:19 -0000 On Saturday, 29 March 2014, at 9:44 am, Tamas Blummer wrote: > I used Shamir's Secret Sharing to decompose a seed for a BIP32 master key, that is I think more future relevant than a single key. > Therefore suggest to adapt the BIP for a length used there typically 16 or 32 bytes and have a magic code to indicate its use as key vs. seed. I have expanded the BIP so that it additionally applies to BIP32 master seeds of sizes 128, 256, and 512 bits. https://github.com/whitslack/btctool/blob/bip/bip-xxxx.mediawiki The most significant change versus the previous version is how the coefficients of the polynomials are constructed. Previously they were SHA-256 digests. Now they are SHA-512 digests, modulo a prime number that is selected depending on the size of the secret.