EulerCoin: Earn digital tokens by solving difficult mathematical Project Euler problems!

Today I’m going to show you something I built during the ETHWaterloo hackathon this weekend.

ETHWaterloo is a hackathon themed around the cryptocurrency Ethereum, which is gaining a lot of traction lately. You have to build something using Ethereum technology, and you can listen to many talks given by experts in the cryptocurrency community. It was a great way to learn more about this new blockchain technology.

vitalik.jpgAbove: Ethereum founder Vitalik Buterin speaking in the opening ceremony

The hackathon opened with a series of talks. I used to be good friends with Vitalik back in first year of university, but haven’t talked to him much after he dropped out of university to work on Ethereum. It was good to see him in person again at this hackathon.

After the opening ceremony, we went to a few tutorials on how to set up the Solidity environment, then brainstormed ideas for what to build. Eventually, we came up with the this:

logo.pngEulerCoin: our new Ethereum-based ICO

We often hear the media describe Bitcoin as “computers solving hard math problems to generate money”. Well, we made a new cryptocurrency, Eulercoin, where tokens are created by correctly submitting the answers to Project Euler problems!

So how does this work?

  • EulerCoin is implemented as a Ethereum smart contract that runs on the blockchain. A user submits answers to the smart contract, which then tries to submit it to Project Euler. If it’s correct, the user is awarded some EulerCoin.
  • Correct answers are recorded on the blockchain forever so anyone can use it to cheat on Project Euler and access the solution forums.
  • For each problem, only the first submitter gets awarded EulerCoin. The amount is larger if the problem has fewer solvers (meaning it’s a harder problem).

I used to maintain a list of Project Euler answers since 2009, but recently it’s been hard to convince people to post their answers publicly. Something like EulerCoin would incentivize people to contribute their answers.

After working on it for a day or so, we got a prototype working:

screenshot.pngAbove: Screenshot of EulerCoin prototype

Here’s a simple web UI, where clicking “Submit” opens up Metamask to initiate an Ethereum transaction. To avoid actually spamming Project Euler for a hackathon project, we mocked up the answer-checking component, but everything else works.


This was the first time programming in Ethereum / Solidity for all of us, so it was a novel experience. After doing this hackathon, I have a much better understanding of what Ethereum does. Bitcoin is digital currency that can only be transferred and not much else. Ethereum is a whole platform where you can run your own custom, Turing-complete smart contracts, all on the blockchain.

Ethereum also has some major limitations that may hinder widespread adoption. Here’s a few facts about Ethereum that I was surprised to learn:

  • All Solidity code is run once by everybody in the blockchain. This is a big scalability problem — imagine that when you buy some coffee, everyone in the world from Canada to France to Vietnam has to process this fact! To sync an Ethereum node, you have to have downloaded a blockchain containing every Ethereum transaction from the beginning of time — too much data for my laptop to handle. This also means that storing even small amounts of data on the blockchain can get incredibly expensive.
  • All data stored in the blockchain is visible to everybody. Because of this, it’s quite difficult to maintain any kind of privacy — this was a problem we ran into for one of our ideas. You can try encryption, but where to store the keys? If you put the keys on the blockchain, then anyone can see it, and you’re back to square one. There are some ideas of using fancy cryptography like ring signatures to keep privacy in limited situations, but these ideas aren’t quite mature yet.

I’m curious to see how Ethereum will solve these big problems in the upcoming years.


22553486_10214254283333445_746148568_o.jpgAbove: Team EulerCoin (Left to Right: Andrei Danciulescu, Chuyi Liu, Shala Chen, Me)

Our submission didn’t make the final round of judging, but we had a good time. Before the closing ceremony, our team gathered for a group photo.

That’s it for now. I’m not sure if I want to invest my own money into Ethereum just yet, but certainly I will read more about cryptocurrencies. Bubble or not, the mathematical ideas and technologies are worth looking into.

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