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 1WNpuI-0006pt-9F for bitcoin-development@lists.sourceforge.net; Wed, 12 Mar 2014 20:37:42 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.216.177 as permitted sender) client-ip=209.85.216.177; envelope-from=will.yager@gmail.com; helo=mail-qc0-f177.google.com; Received: from mail-qc0-f177.google.com ([209.85.216.177]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WNpuH-0001nR-Bb for bitcoin-development@lists.sourceforge.net; Wed, 12 Mar 2014 20:37:42 +0000 Received: by mail-qc0-f177.google.com with SMTP id w7so80227qcr.8 for ; Wed, 12 Mar 2014 13:37:35 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.140.36.200 with SMTP id p66mr54530702qgp.54.1394656655829; Wed, 12 Mar 2014 13:37:35 -0700 (PDT) Received: by 10.140.31.135 with HTTP; Wed, 12 Mar 2014 13:37:35 -0700 (PDT) In-Reply-To: <5320C27B.8090205@gk2.sk> References: <44fcb02b-3784-45a6-816a-312c78d940cd@me.com> <5320B7F1.8060701@gk2.sk> <5320BDD1.50001@gk2.sk> <5320C27B.8090205@gk2.sk> Date: Wed, 12 Mar 2014 15:37:35 -0500 Message-ID: From: William Yager To: Pavol Rusnak Content-Type: multipart/alternative; boundary=001a11c13c808e0d2504f46ecec7 X-Spam-Score: -0.6 (/) 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 (will.yager[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message -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: 1WNpuH-0001nR-Bb Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] [RFC] Proposal: Base58 encoded HD Wallet root key with optional encryption 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: Wed, 12 Mar 2014 20:37:42 -0000 --001a11c13c808e0d2504f46ecec7 Content-Type: text/plain; charset=ISO-8859-1 On Wed, Mar 12, 2014 at 3:24 PM, Pavol Rusnak wrote: > On 03/12/2014 09:10 PM, William Yager wrote: > > implement this is to allow semi-trusted devices (like desktop PCs) to do > > all the "heavy lifting". The way the spec is defined, it is easy to have > a > > more powerful device do all the tough key stretching work without > > significantly compromising the security of the wallet. > > By disclosing "preH" to compromised computer (between steps 4 and 5) you > make further steps 5-9 quite less important. > > Yes, that was my chief complaint as well. A compromised computer removes most of the extra security offered by key stretching (should you choose to outsource the bulk of your key stretching). However, I think we have a good compromise, which is the inclusion of a number of PBKDF2-HMAC-SHA512 based KDFs. For anyone who doesn't want to trust any external device, but also wants to use memory-contrained devices (that group of people includes me), PBKDF2-HMAC-SHA512 is very easy to implement even on devices that only have a few kB of RAM, and even though our number of rounds is very aggressive (2^16 and 2^21), it will still run in reasonable time even on very slow embedded ARM processors. Will --001a11c13c808e0d2504f46ecec7 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
On Wed, Mar 12, 2014 at 3:24 PM, Pavol Rusnak <stick@gk2.sk> wrote:
On 03/12/2014 09:10 PM, William Yager wrote:
> implement this is to allow semi-trusted devices (like desktop PCs) to = do
> all the "heavy lifting". The way the spec is defined, it is = easy to have a
> more powerful device do all the tough key stretching work without
> significantly compromising the security of the wallet.

By disclosing "preH" to compromised computer (between steps= 4 and 5) you
make further steps 5-9 quite less important.


Yes, that was my chief= complaint as well. A compromised computer removes most of the extra securi= ty offered by key stretching (should you choose to outsource the bulk of yo= ur key stretching).

However, I think we have a good compromise, which is th= e inclusion of a number of PBKDF2-HMAC-SHA512 based KDFs. For anyone who do= esn't want to trust any external device, but also wants to use memory-c= ontrained devices (that group of people includes me), PBKDF2-HMAC-SHA512 is= very easy to implement even on devices that only have a few kB of RAM, and= even though our number of rounds is very aggressive (2^16 and 2^21), it wi= ll still run in reasonable time even on very slow embedded ARM processors.<= /div>

Will

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