Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WNq61-0001YZ-G1 for bitcoin-development@lists.sourceforge.net; Wed, 12 Mar 2014 20:49:49 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.216.175 as permitted sender) client-ip=209.85.216.175; envelope-from=will.yager@gmail.com; helo=mail-qc0-f175.google.com; Received: from mail-qc0-f175.google.com ([209.85.216.175]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WNq60-0002Ea-H0 for bitcoin-development@lists.sourceforge.net; Wed, 12 Mar 2014 20:49:49 +0000 Received: by mail-qc0-f175.google.com with SMTP id e16so101093qcx.6 for ; Wed, 12 Mar 2014 13:49:43 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.140.29.38 with SMTP id a35mr55890656qga.55.1394657383138; Wed, 12 Mar 2014 13:49:43 -0700 (PDT) Received: by 10.140.31.135 with HTTP; Wed, 12 Mar 2014 13:49:43 -0700 (PDT) In-Reply-To: <5320C6C7.9040602@gk2.sk> References: <44fcb02b-3784-45a6-816a-312c78d940cd@me.com> <5320B7F1.8060701@gk2.sk> <5320BDD1.50001@gk2.sk> <5320C27B.8090205@gk2.sk> <5320C6C7.9040602@gk2.sk> Date: Wed, 12 Mar 2014 15:49:43 -0500 Message-ID: From: William Yager To: Pavol Rusnak Content-Type: multipart/alternative; boundary=001a113b40fae7c95404f46ef9ae 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: 1WNq60-0002Ea-H0 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 20:49:49 -0000 --001a113b40fae7c95404f46ef9ae Content-Type: text/plain; charset=ISO-8859-1 On Wed, Mar 12, 2014 at 3:42 PM, Pavol Rusnak wrote: > On 03/12/2014 09:37 PM, William Yager wrote: > > (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. > > To give you some numbers: TREZOR (120MHz ARM) does 1024 rounds of > PBKDF2-HMAC-SHA512 in around 1 second. > > So 2^16 is around one minute, 2^21 is around half an hour. > > Precisely. And since the target of this BIP is generally storage wallets (just like BIP 0038), we figured these were reasonable time scales for encryption/decryption on slow devices. Let's say you're implementing a Raspberry Pi based cold wallet printer. Having the user wait 10 seconds to several minutes is not unreasonable for a one-time activity, especially when at least this much time is used to generate entropy, print the wallet, etc. The same goes for phones. If you're importing a heavily encrypted wallet into your device, the user won't mind waiting a few seconds or even a few minutes. Plus, as an added bonus, the amount of time it will take to encrypt/decrypt is highly deterministic, so it's easy to add a nice progress bar to a UI. Will --001a113b40fae7c95404f46ef9ae Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
On Wed, Mar 12, 2014 at 3:42 PM, Pavol Rusnak <stick@gk2.sk> wrote:
On 03/12/2014 09:37 PM, William Yager wrote:
> (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 tho= ugh
> 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.

To give you some numbers: TREZOR (120MHz ARM) does 1024 rounds of
PBKDF2-HMAC-SHA512 in around 1 second.

So 2^16 is around one minute, 2^21 is around half an hour.

<= br>
Precisely. And since the target of this BIP is generally stor= age wallets (just like BIP 0038), we figured these were reasonable time sca= les for encryption/decryption on slow devices.

Let's say you're implementing a Raspberry Pi ba= sed cold wallet printer. Having the user wait 10 seconds to several minutes= is not unreasonable for a one-time activity, especially when at least this= much time is used to generate entropy, print the wallet, etc.

The same goes for phones. If you're importing a hea= vily encrypted wallet into your device, the user won't mind waiting a f= ew seconds or even a few minutes.

Plus, as an adde= d bonus, the amount of time it will take to encrypt/decrypt is highly deter= ministic, so it's easy to add a nice progress bar to a UI.

Will
--001a113b40fae7c95404f46ef9ae--