From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Z3Uqq-0006kY-Qt for bitcoin-development@lists.sourceforge.net; Fri, 12 Jun 2015 19:42:52 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.213.65 as permitted sender) client-ip=209.85.213.65; envelope-from=swansontec@gmail.com; helo=mail-yh0-f65.google.com; Received: from mail-yh0-f65.google.com ([209.85.213.65]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Z3Uqp-0006To-Mp for bitcoin-development@lists.sourceforge.net; Fri, 12 Jun 2015 19:42:52 +0000 Received: by yhab6 with SMTP id b6so2831595yha.2 for ; Fri, 12 Jun 2015 12:42:46 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.13.200.67 with SMTP id k64mr21172876ywd.125.1434138166244; Fri, 12 Jun 2015 12:42:46 -0700 (PDT) Received: by 10.37.60.134 with HTTP; Fri, 12 Jun 2015 12:42:46 -0700 (PDT) In-Reply-To: References: Date: Fri, 12 Jun 2015 12:42:46 -0700 Message-ID: From: William Swanson To: James Poole Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 (swansontec[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: 1Z3Uqp-0006To-Mp Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Bip 32 Question 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 Jun 2015 19:42:52 -0000 The `n` is the curve order, as shown here: https://en.bitcoin.it/wiki/Secp256k1 This step is necessary to keep you on the curve. The secp256k1_ec_privkey_tweak_add function from libsecp256k1 handles this automatically, but if you use OpenSSL or some non-EC math library, you probably have to do it yourself. -William On Fri, Jun 12, 2015 at 11:22 AM, James Poole wrote: > Looking at the BIP32 definition, I hit a line that I would appreciate > clarification on. > > https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki > > Under the section "Private parent key =E2=86=92 private child key" there = is a step: > > "The returned child key ki is parse256(IL) + kpar (mod n)." > > Can someone help me understand what "n" is in the context of this algorit= hm? > I very well could be looking right at it, but wanted to double check if I= am > missing something. > > Thanks, > James