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 1YsTxC-00049i-Mt for bitcoin-development@lists.sourceforge.net; Wed, 13 May 2015 10:31:54 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 74.125.82.52 as permitted sender) client-ip=74.125.82.52; envelope-from=alex.mizrahi@gmail.com; helo=mail-wg0-f52.google.com; Received: from mail-wg0-f52.google.com ([74.125.82.52]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1YsTxB-0001IR-UW for bitcoin-development@lists.sourceforge.net; Wed, 13 May 2015 10:31:54 +0000 Received: by wgin8 with SMTP id n8so38765524wgi.0 for ; Wed, 13 May 2015 03:31:47 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.180.73.202 with SMTP id n10mr13554119wiv.0.1431513107904; Wed, 13 May 2015 03:31:47 -0700 (PDT) Received: by 10.27.102.73 with HTTP; Wed, 13 May 2015 03:31:47 -0700 (PDT) In-Reply-To: References: <5550D8BE.6070207@electrum.org> <5551F376.4050008@electrum.org> <555210AF.3090705@electrum.org> <55531E19.3090503@electrum.org> Date: Wed, 13 May 2015 13:31:47 +0300 Message-ID: From: Alex Mizrahi To: Bitcoin Dev Content-Type: multipart/alternative; boundary=f46d0435c0f449be660515f41e1d 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 (alex.mizrahi[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: 1YsTxB-0001IR-UW Subject: Re: [Bitcoin-development] Long-term mining incentives 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, 13 May 2015 10:31:54 -0000 --f46d0435c0f449be660515f41e1d Content-Type: text/plain; charset=UTF-8 > With POW, a new node only needs to know the genesis block (and network > rules) to fully determine which of two chains is the strongest. > But this matters if a new node has access to the globally strongest chain. If attacker is able to block connections to legitimate nodes, a new node will happily accept attacker's chain. So PoW, by itself, doesn't give strong security guarantees. This problem is so fundamental people avoid talking about it. In practice, Bitcoin already embraces "weak subjectivity" e.g. in form of checkpoints embedded into the source code. So it's hard to take PoW purists seriously. --f46d0435c0f449be660515f41e1d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
=C2=A0
With POW, a new node only need= s to know the genesis block (and network rules) to fully determine which of= two chains is the strongest.
=
But this matters if a new node has access to the globally st= rongest chain.
If attacker is able to block connections to legiti= mate nodes, a new node will happily accept attacker's chain.
=
So PoW, by itself, doesn't give strong security guarante= es. This problem is so fundamental people avoid talking about it.

In practice, Bitcoin already embraces "weak subjectivi= ty" e.g. in form of checkpoints embedded into the source code. So it&#= 39;s hard to take PoW purists seriously.
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