From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WTpC2-0003Zh-32 for bitcoin-development@lists.sourceforge.net; Sat, 29 Mar 2014 09:04:46 +0000 X-ACL-Warn: Received: from qmta02.westchester.pa.mail.comcast.net ([76.96.62.24]) by sog-mx-1.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1WTpC1-0007sV-7a for bitcoin-development@lists.sourceforge.net; Sat, 29 Mar 2014 09:04:46 +0000 Received: from omta07.westchester.pa.mail.comcast.net ([76.96.62.59]) by qmta02.westchester.pa.mail.comcast.net with comcast id jLrA1n0061GhbT851LrAbz; Sat, 29 Mar 2014 08:51:10 +0000 Received: from crushinator.localnet ([IPv6:2601:6:4800:47f:219:d1ff:fe75:dc2f]) by omta07.westchester.pa.mail.comcast.net with comcast id jLr91n00H4VnV2P3TLr9e8; Sat, 29 Mar 2014 08:51:10 +0000 From: Matt Whitlock To: Tamas Blummer Date: Sat, 29 Mar 2014 04:51:09 -0400 Message-ID: <1533279.gyh3J7MHJl@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 [76.96.62.24 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: 1WTpC1-0007sV-7a Cc: bitcoin-development@lists.sourceforge.net 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 09:04:46 -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. Master keys of 32 bytes would work as-is, as ordinary private keys are also 32 bytes. Secrets of other lengths could be supported if the function that generates a[i] from a[i-1] (which is presently SHA-256) were replaced with a function having parameterized output length, such as scrypt. Base58Check encodings of shares for secrets of lengths other than 32 bytes would have prefixes other than "SS", but that's not a huge concern. I suspect 32 bytes would be the most common secret length anyway, wouldn't you?