From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 3D301AAE for ; Sat, 11 Jul 2015 10:39:40 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-qk0-f176.google.com (mail-qk0-f176.google.com [209.85.220.176]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 2A6A132 for ; Sat, 11 Jul 2015 10:39:39 +0000 (UTC) Received: by qkbp125 with SMTP id p125so223041471qkb.2 for ; Sat, 11 Jul 2015 03:39:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:cc :content-type; bh=yUf/uM6PVZz4Xn+K3+yeb7qzGPF+PPB3GcQzqxl1dgw=; b=y7+Mpmtp55XogUSxl4QD8/MatiwwUsEdEPrL9D3fyFpgrR4nsYkiSi6fTzTal1tY/S 3KjaFmEinrc2OM15nx+pASvZ1kUNLhw/0MGeqyFISXi3pf3oUcS5WK6Ppo8Dcq9+XTNE pR0LJKS0wP08kysyJAuIQL519M7fOUQTtnJFubLW8mT4aR42L6yomVOzEasM4Q8gvGWQ cuNidyLfdoCW5Mj6zrbJ8lHrQuv0qKYkwFzONC9SP27fVJVdt5aTqTwKGuH28LDknjKa gsr6nk2/Ub7R/z9axSJZd9BmWW+AZz9wAoYqZ+JiEUF4dQpYVoX6oDI1hqPrrX+apLAP IGfg== MIME-Version: 1.0 X-Received: by 10.55.43.75 with SMTP id r72mr40066688qkh.80.1436611178386; Sat, 11 Jul 2015 03:39:38 -0700 (PDT) Received: by 10.140.93.162 with HTTP; Sat, 11 Jul 2015 03:39:38 -0700 (PDT) In-Reply-To: References: Date: Sat, 11 Jul 2015 11:39:38 +0100 Message-ID: From: Tier Nolan Cc: bitcoin-dev@lists.linuxfoundation.org Content-Type: multipart/alternative; boundary=001a1147732ef7d9af051a971a0d X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,HTML_MESSAGE,MISSING_HEADERS, RCVD_IN_DNSWL_LOW autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] SPV Mining reveals a problematic incentive issue. X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Jul 2015 10:39:40 -0000 --001a1147732ef7d9af051a971a0d Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Sat, Jul 11, 2015 at 10:24 AM, Jorge Tim=C3=B3n wrote= : > I think it would be more rational for them to keep mining on top of the > old block until they've fully validated the new block (which shouldn't ta= ke > so long anyway), even if this slightly increases the orphan rate. Increased orphan rate means that the network is (slightly) less secure. If miners have a 5% orphan rate, then an attacker can launch a 51% attack with 49% of the network. It isn't a massive difference, but it is there. As long as miners switch back to non-SPV mining after a timeout, SPV-mining is safe for everyone. The average cost to the miner from building on an invalid block is small, as long as invalid blocks only happen rarely. Miners still have an incentive to do full validation, so that they can include transactions and get transaction fees. SPV-mining is to prevent hashing hardware from having to waste power when it isn't needed. It may be less of a problem if (when?) electricity costs dominate hardware capital costs. --001a1147732ef7d9af051a971a0d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Sat, Jul 11, 2015 at 10:24 AM, Jorge Tim=C3=B3n &l= t;jtimon@jtimon.cc> wrote:
I think it would be m= ore rational for them to keep mining on top of the old block until they'= ;ve fully validated the new block (which shouldn't take so long anyway)= , even if this slightly increases the orphan rate.

Increased orphan rate means that the netwo= rk is (slightly) less secure.

If miners have a= 5% orphan rate, then an attacker can launch a 51% attack with 49% of the n= etwork.

It isn't a massive difference, but it is ther= e.

As long as miners switch back to non-SPV mining after = a timeout, SPV-mining is safe for everyone.

The average c= ost to the miner from building on an invalid block is small, as long as inv= alid blocks only happen rarely.

Miners still have an inc= entive to do full validation, so that they can include transactions and get= transaction fees.

SPV-mining is to= prevent hashing hardware from having to waste power when it isn't need= ed.

It may be less of a problem if = (when?) electricity costs dominate hardware capital costs.
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