From mboxrd@z Thu Jan 1 00:00:00 1970 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 1X30iq-0004bH-3y for bitcoin-development@lists.sourceforge.net; Fri, 04 Jul 2014 10:28:04 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 74.125.82.170 as permitted sender) client-ip=74.125.82.170; envelope-from=andyparkins@gmail.com; helo=mail-we0-f170.google.com; Received: from mail-we0-f170.google.com ([74.125.82.170]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1X30io-0000G6-D6 for bitcoin-development@lists.sourceforge.net; Fri, 04 Jul 2014 10:28:04 +0000 Received: by mail-we0-f170.google.com with SMTP id w61so1475552wes.15 for ; Fri, 04 Jul 2014 03:27:56 -0700 (PDT) X-Received: by 10.180.82.7 with SMTP id e7mr55731421wiy.74.1404469674977; Fri, 04 Jul 2014 03:27:54 -0700 (PDT) Received: from momentum.localnet ([91.84.15.31]) by mx.google.com with ESMTPSA id fn1sm77658228wib.18.2014.07.04.03.27.53 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 04 Jul 2014 03:27:54 -0700 (PDT) From: Andy Parkins To: Bitcoin Dev Date: Fri, 04 Jul 2014 11:27:51 +0100 Message-ID: <10566815.3CllqoMfON@momentum> User-Agent: KMail/4.12.4 (Linux/3.10-2-amd64; KDE/4.13.1; x86_64; ; ) MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" 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 (andyparkins[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: 1X30io-0000G6-D6 Subject: [Bitcoin-development] ASIC-proof mining 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, 04 Jul 2014 10:28:04 -0000 Hello, I had a thought after reading Mike Hearn's blog about it being impossible to have an ASIC-proof proof of work algorithm. Perhaps I'm being dim, but I thought I'd mention my thought anyway. It strikes me that he's right that it's impossible for any algorithm to exist that can't be implemented in an ASIC. However, that's only because it's trying to pick an algorithm that is CPU bound. You could protect against ASCI mining (or rather, make it irrelevant that it was being used) by making the algorithm IO-bound rather than CPU-bound. For example, what if the proof-of-work hash for a block were no longer just "hash of block", which contains the hash of the parent block, but instead were hash of [NEW_BLOCK] [ALL_PREVIOUS_BLOCKS] [NEW_BLOCK] [ALL_PREVIOUS_BLOCKS] is now 20GB (from memory) and growing. By prefixing and suffixing the new block, you have to feed every byte of the blockchain through the hashing engine (the prefix prevents you caching the intermediate result). Whatever bus you're using to feed your high speed hashing engine, it will always be faster than the bus -- hence you're now IO-bound, not CPU-bound, and any hashing engine will, effectively, be the same. I'm making the assumption that SHA-256 is not cacheable from the middle outwards, so the whole block-chain _has_ to be transferred for every hash. Apologies in advance if this is a stupid idea. Andy -- Dr Andy Parkins andyparkins@gmail.com