-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 3/2/2014 6:05 AM, James A. Donald wrote: > On 2014-03-02 11:29, s...@sky-ip.org wrote: >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 >> >> Hi, >> >> I want to build a marketplace where users can exchange bitcoin >> for fiat currencies without having to go through a centralized >> escrow or exchanger (directly user-to-user). This can be done by >> bitcoin multisign option (contracts) where 2 users can agree on a >> mediator and proceed with a transaction. >> >> The problem is: if the users don't go through a centralized >> escrow or exchanger and they don't add funds or add bitcoins to >> their accounts, how can we verify the authenticity of sell or buy >> postings and build a strong and accurate order book, without >> users being able to abuse it by posting abusive sell or buy >> offers which will break the supply and demand calculation for >> price determination. This is a real possible vulnerability since >> it's not a centralized system and users do not deposit funds in >> their accounts, you cannot verify if the user has or doesn't have >> the bitcoins or the fiat currency. > > You can verify that the user has the bitcoins. > > For the fiat currency, need a reputation system that looks like > silk road or ebay, but is decentralized. This is a problem, since > what is to stop someone from building reputation by doing a > thousand fake transactions with himself? > > This sybil attack could be defeated by clustering analysis, > identifying groups that give positive ratings to each other, but do > not receive positive ratings from outsiders. > >
That sounds about right. So, to repeat, the system will create random groups of N users, chosen randomly by the system (the users cannot choose a group they want to be a part of) and reputation will be built only by people inside that group, nobody from outside will be able to positive or negative feedback? In this case, the chances for an malicious person to create 1000 fake accounts to transact with himself and all of them to be part of the same group are considerably smaller. Not inexistent, though. But in centralized exchangers, what prevents users from doing this? If a malicious person is willing and can afford to lose the exchanger fee of .5 or .7 or whatever, he can transact with himself manipulating the price with just the cost of the exchanger fee? I doubt the current exchangers have any protection against this what do you think? - -- PGP Public key: http://www.sky-ip.org/s...@sky-ip.org.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) iQEcBAEBAgAGBQJTEyNgAAoJEIN/pSyBJlsRzSwIAMDwOJPPRaGxX5NjGDviO3Tu tD9opHU2S6mb820f31D0o+XlwKx+DA2yZ3M8GmGsEjEbESH//kJT2Dcvnpd4TLoC TwS2mfyEZDpWrdZuC/uULj5ZVl6PGDs+KVGvNNJwuuosUa9Ni8PHboyhW/sf5unJ xQGHfLtDnUu2T+w1fklvfOj+73nonf8499ueQCLGGaUSVtG2sTKRmb+RZVKwX588 6o06FvT+TbASTs+9K74gh/S/l9F9lmGlKcqVFFbsdU1124aQy03TiLTbRhrABCY/ E26AWjWW+3aPoK9Y244yi29KmncBcdvuO0A7OteyF6f9h3OcyCsQQd0s+gXUKDA= =PCLW -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Flow-based real-time traffic analytics software. Cisco certified tool. Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer Customize your own dashboards, set traffic alerts and generate reports. Network behavioral analysis & security monitoring. All-in-one tool. http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk _______________________________________________ bitcoin-list mailing list bitcoin-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-list
