The concept of price stable cryptocurrencies has been on my mind a lot because I’m working on a peer-to-peer marketplace. While cryptocurrency marketplaces have struggled with price instability, a price-stable cryptocurrency could offer comfort to users and merchants who are not interested in speculating. I was happy to learn that there are multiple groups working very hard to make such a reality come true. This post is about one particularly novel strategy being utilized by MakerDao and BitShares: Contract for Differences or CFDs.

While the mechanisms of this strategy can be complicated, there are a few main takeaways:

  1. It requires an honest price feed that will report changes in exchange rates
  2. It allows the creation of token pegged to any price index or asset, without holding the asset being pegged to
    1. You could peg a token to the USD without any reserves of USD
    2. You could peg a token to the Big Mac Index without holding any reserves of Big Macs

Lets assume there’s a cryptocurrency enthusiast named Harry. Harry’s friends call him High-Risk-High-Reward Harry because he has a high tollerance for risk. Harry really likes reading the latest news in the crypto space and decides he can put his knowledge to good use by becoming a speculator. He goes to a ETH/USD exchange where he starts a bank transfer of $100USD. Once the bank transfer is complete, his exchange account holds $100USD and $0ETH.

On one particular day, Harry reads about a new development in the Ethereum world that he thinks could radically increase the value of ether. He goes to his exchange and immediately converts the entirety of his portfolio from USD to ETH. Harry now holds $0USD and $100ETH

It turns out, Harry’s prediction was right and his decision to convert USD to ETH was very wise. The value of ether doubles. Harry’s exchange account now holds $0USD and $200ETH

Harry looks at the market, and he concludes that ether’s current bull run isn’t over yet. He wants to buy more ETH, but he doesn’t have any more USD in his account. He could start a bank transfer, however that will take 3 days and he thinks the bull run might be over by then.

Instead of buying more USD, Harry can create a contract for difference, or CFD, with another investor, who we will name Nelly. Nelly’s friends call him No-Risk-No-Reward Nelly because he likes stability.

Unlike Harry, Nelly isn’t really interested in speculating on the day-to-day of ether. He just wants to make sure the value of the money in his account stays stable.

Harry and Nelly agree to a CFD that goes like this:

  1. Harry will put up his $200ETH as collateral into an escrow
  2. Nelly will put up his $100ETH of collateral into the same escrow
  3. The CFD will end in 24 hours at which point
    1. The escrow will send $100ETH of collateral will be sent to Nelly
    2. The escrow will send the remainder of the collateral to Harry

Note that this CFD exists entirely on the blockchain. The escrow is automated and there is no risk of the escrow stealing funds.

Lets take a look at the value of the CFD under two scenarios. In the first scenario, the price of ETH in USD doubles. In the second scenario, the price of ETH in USD halves.

  1. If the price of ETH doubles, the value of the collateral in the CFD doubles from $300ETH to $600ETH. Since Nelly will be returned $100ETH, Harry will be returned $500ETH.
  2. If the price of ETH halves, the value of the collateral in the CFD halves from $300ETH to $150ETH. Since Nelly’s will be returned $100ETH, Harry will be returned a mere $50ETH

While the value of the CFD to Harry is volatile, the value of the CFD to Nelly is completely known. He will always receive $100ETH.

But wait!

What if the value of ETH drops so much that even the collateral cannot cover it?

While we have $300ETH of collateral, a very severe drop in the price of ETH could make it so that Nelly does not receive his original $100ETH. This is protected against automatically by the escrow service, who prematurely ends the existing CFD and automatically rolls Nelly’s $100ETH into a new CFD if there is a possibility of a default. In such a scenario, Harry might not be returned any of his original collateral.

Creating the Currency

Now Nelly has a CFD provably worth $100ETH. Rather then forcing Nelly to claim the CFD, we could send a ticket to Nelly that allows him (or anyone else who presents that ticket) to claim the CFD. In turn, Nelly could sell that ticket to whoever he likes.

As these tickets grow in quantity, they eventually become a currency. Every ticket holder knows their ticket corresponds to a CFD worth $100ETH.


All of this assumes that the market for CFDs is liquid enough to support the tickets. When one CFD ends, the collateral returned from the ticket has to be rolled over into a new CFD. If ether has been stable or declining for a period of long period of time, the High-Risk-High-Reward Harrys of the world might decide to wait it out. If enough Harrys quit the market, the tickets no longer have any backing.

There’s some interesting ways to provide insurance against this sort of scenario, but thats beyond the scope of this post.


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