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[92.251.83.90]) by mx.google.com with ESMTPSA id m54sm16479481eex.2.1969.12.31.16.00.00 (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 01 Oct 2013 12:11:45 -0700 (PDT) Received: by netbook (Postfix, from userid 1000) id 8A8862E0B63; Tue, 1 Oct 2013 21:11:44 +0200 (CEST) Received: by flare (hashcash-sendmail, from uid 1000); Tue, 1 Oct 2013 21:11:43 +0200 Date: Tue, 1 Oct 2013 21:11:43 +0200 From: Adam Back <adam@cypherspace.org> To: Mark Friedenbach <mark@monetize.io> Message-ID: <20131001191143.GA16116@netbook.cypherspace.org> References: <CAKaEYhLvqT6nkbupEEgR1d9dMP4-pA7xQbBqPDbREiDDV7c0rQ@mail.gmail.com> <2c70dbfc173749cf4198c591f19a7d33@astutium.com> <CAH+ZByHs00+Cpx5bwybgV3G9=CBfHaHKg7AV9ytywKNAjFVM6g@mail.gmail.com> <CABsx9T29T+thSeF-xVk+prfeO7ZJQbX=n=tAURqEKQsVtcBpQg@mail.gmail.com> <20130929093708.GA16561@netbook.cypherspace.org> <5248680C.60404@monetize.io> <20131001142603.GA9208@netbook.cypherspace.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20131001142603.GA9208@netbook.cypherspace.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Hashcash: 1:20:131001:mark@monetize.io::ykSiHrXFHuytHKL6:01Rxm X-Hashcash: 1:20:131001:bitcoin-development@lists.sourceforge.net::vrjmBlYcVdp1O gyn:000000000000000000001wuU X-Hashcash: 1:20:131001:adam@cypherspace.org::BZ1SCJDOWLGT8Tla:00000000000000000 0000000000000000000000003nMj X-Spam-Score: -1.5 (-) 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 (adam.back[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [URIs: bitcointalk.org] X-Headers-End: 1VR5MO-0005VB-2L Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net> Subject: Re: [Bitcoin-development] homomorphic coin value (validatable but encrypted) (Re: smart contracts -- possible use case? yes or no?) X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: <bitcoin-development.lists.sourceforge.net> List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>, <mailto:bitcoin-development-request@lists.sourceforge.net?subject=unsubscribe> List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development> List-Post: <mailto:bitcoin-development@lists.sourceforge.net> List-Help: <mailto:bitcoin-development-request@lists.sourceforge.net?subject=help> List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>, <mailto:bitcoin-development-request@lists.sourceforge.net?subject=subscribe> X-List-Received-Date: Tue, 01 Oct 2013 19:11:54 -0000 Err actually not (efficient) I made a mistake that came out when I started writing it up about how the t parameter in the proof relates to bitcoin precision and coin representation (I thought t=2, but t=51). Damn! Back to the not so efficient version (which is more zerocoin-esque in size/cost), or the more experimental Schoenmaker non-standard p, q non EC one, or other creative ideas to change the coin representation to simplify the proof (of which this was a failed attempt). See the bitcointalk thread for details. https://bitcointalk.org/index.php?topic=305791.new#new Adam On Tue, Oct 01, 2013 at 04:26:03PM +0200, Adam Back wrote: >On Sun, Sep 29, 2013 at 10:49:00AM -0700, Mark Friedenbach wrote: >>This kind of thing - providing external audits of customer accounts >>without revealing private data - would be generally useful beyond >>taxation. If you have any solutions, I'd be interested to hear them >>(although bitcoin-dev is probably not the right place yet). > >Thanks for providing the impetus to write down the current state, the >efficient version of which I only figured out a few days ago :) > >I have been researching this for a few months on and off, because it seems >like an interesting construct in its own right, a different aspect of >payment privacy (eg for auditable but commercial sensistive information) but >also that other than its direct use it may enable some features that we have >not thought of yet. > >I moved it to bitcointalk: > >https://bitcointalk.org/index.php?topic=305791.new#new > >Its efficient finally (after many dead ends): approximately 2x cost of >current in terms of coin size and coin verification cost, however it also >gives some perf advantages back in a different way - necessary changes to >schnorr (EC version of Schnorr based proofs) allow n of n multiparty sigs, >or k of n multiparty sigs for the verification cost and signature size of >one pair of ECS signatures, for n > 2 its a space and efficiency improvement >over current bitcoin. > >Adam