Using The Nash Equilibrium and Mutually Assured Destruction To Bypass Bitcoin Currency Exchanges

bitcoin-225A fascinating concept has been created by software developer Seong Yup Yoo.  Mr. Yoo has created a website that allows people to exchange fiat money for Bitcoins directly with each other without having to use a third party exchange. He has accomplished this task by incorporating the concepts of mutually assured destruction and the Nash equilibrium.

The problem facing two people in a direct exchange is that no one wants to send their money first.  Let’s go through a simple scenario.  Let’s suppose there is a forum where people post Bitcoins for sale like bitcoin-otc, and I am interested in buying Bitcoins from one of the users.  I message a person who is selling 10 Bitcoins asking him to do a swap of my dollars for his Bitcoins.  If I send him money through PayPal, how do I know he will send me the coins?  If he sends me the coins, how does he know I will wire him the fiat money on PayPal?  Clearly this ends in a stalemate with neither person willing to risk sending the money first.

The site NashX attempts to address this problem by having people risk Bitcoins for destruction before initiating a trade.  Here’s an example of how it works.  Both the buyer and the seller create accounts on NashX.  Both the buyer and the seller load Bitcoins into their NashX accounts.  When a seller wishes to sell his Bitcoins for cash, he will put up an offer that looks something like this:

“I will risk 20 Bitcoins in order to sell 10 Bitcoins for $1000 USD”

The buyer will then respond by accepting this deal, and putting up 20 Bitcoins of his own.  So both the buyer and the seller now have 20 Bitcoins at stake in this deal.  The buyer then messages the seller to get his PayPal information and sends him the money on PayPal.  If the buyer fails to send the seller his cash, the seller can destroy the deal, sending all 40 of the “at risk” coins into a “blackhole” address where no one will ever have access to those coins.  Presently the site is setup to send the destroyed coins to the miners who processed the transaction, but Yoo is considering changing this to a blackhole address.

By doubling the amount being offered for sale and putting that amount up as “at risk funds” the exchange stays within the Nash equilibrium.  By pairing this concept with mutually assured destruction, trades can be made with a high level of confidence that each player will hold up his end of the bargain. This system eliminates the need to have a web of trust, such as the one presently in place at bitcoin-otc.

If one party only has a small amount of Bitcoins to work with, but wants to buy or sell a lot more, the solution is to simply do several smaller transactions.  So my 10  Bitcoin example might take place with ten 1 Bitcoin transactions using a 2 Bitcoin risk fund for each trade.  Since each party already has each other’s details, these exchanges can take place in a fairly rapid succession.

While the site is still in beta, I can already tell that the concept has a tremendous amount of promise.  I expect to see similar sites like this one popping up all over the internet.  Sites like this will allow for virtually unlimited currency trading that occurs outside the scope of the heavily regulated and monitored banking industry.  NashX’s trading structure allows for anonymous trades if users wish to go that route, as people could send cash by snail mail if they wanted to, although the seller would still have to provide a mailing address.

Further, given that the prices for coins are entered in a separate data field, it is entirely possible to build up a display of price metrics.  This means that if state actors were to ever shutdown the major Bitcoin exchanges, pricing information could still be obtained from sites like NashX.  Sites like NashX make it virtually impossible for state actors to completely shutdown the Bitcoin network by attacking the weakest link.  As long as pricing information is maintained, trades can continue over the counter.

I encourage Mr. Yoo to open source his code, which would allow people to rapidly build upon the concept, along with making it easier for people to setup similar sites on the Tor network without having to code their own from scratch.

Given that NashX is not tied to any financial institution, a similar site could easily be setup on the Tor network.  If such a site existed on the Tor network, not only could users be assured of their anonymity, it would also completely prevent any state actors from attempting to shutdown the site by legislation.  The Tor network is an encrypted anonymous web network that hosts sites like the Silk Road.

The only downside to this process is that each player must already have Bitcoins before either can initiate a trade.  However, Mr. Yoo stated he is addressing this problem by “NashX taking Cash-At-Bank and sending BTC/LTC directly to their risk fund at BTC-E exchange rates.”  So basically you can wire him money and he will load your account.  While this requires trusting Mr. Yoo, at least you know who he is and where his business is located, which would allow you to file a lawsuit against him if he fails to deliver.

  • Peter Surda

    This is very interesting.

  • Jonathan Jaech

    Thanks I too find this interesting. The same concept would work for all forms of bartering for digital cash, whether or not involving FRNs. For established sellers you don’t even need the risk capital as the seller’s reputation (and the buyer’s) are at stake — witness eBay etc.

  • d

    Step 4: buyer issues a chargeback, and walks away with both the bitcoins and the dollars. Hmm, something is wrong here. In other words, this will only work with non-chargebackable methods. Like cash in person/mail maybe.

    • Yeah, charge backs are possible, but with a charge back at least you know who you are dealing with, which allows for a lawsuit.

      Also, a rating system can be implemented like we see for bitcoin-otc, it’s just that the system makes ratings less necessary.

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  • newmorpheus

    This concept is by fare the most promising concept for exchanging history ever have seen!!!

    I want to start a group of anonymous developers that want to set up this service via TOR. Contact me on

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  • Earl Fox

    I have a question: how about delivery time? What if it will take 2 months to deliver goods? As far as I know nashx destroy funds 30 days after transaction being done, right?