BitcoinHex Smart Contracts

Features

Trustless Compounding Interest
This function is a hybrid of the classic algorithm and looping in order to avoid both gas limit issues and integer overflows.
Merkle Proof Usage
Using root merkle hashes at a specific block number, the contract can verify that a specific Bitcoin UTXO exists. Allowing for a Bitcoin holder to claim tokens.
Elliptic Curve Recovery
Due to Bitcoin and Ethereum using the same elliptic curve, public keys from both blockchains can be used in order to sign data. This means that a bitcoin public key can be verified on an Ethereum smart contract. This is the second component to enabling Bitcoin holders to claim tokens.
ERC20 Compliant
Follows the ERC20 standard, allowing for widespread interaction.
Extensive Testing
On top of regular integration tests, stress tests are needed in order to be sure that there are no integer overflows when calculating compounding interest. Additionally, there are looping functions which needed to be tested in order to have assurances that nothing would be stuck in a broken state due to gas limit issues when looping over arrays.

Languages & Frameworks

Solidity
Used for Smart Contracts
Javascript
Used for integration tests
Mocha & Chai
Truffle
Used as a testing framework
OpenZeppelin
Used for merkle tree and ERC20 functionality

Some Neat Stuff that I Got to Work with

I think the coolest thing that I got to work with and test on this project was using Bitcoin private keys to claim Ethereum based ERC20 tokens. This is possible because both Bitcoin and Ethereum public keys are of the same format. This combined with elliptic curve recovery for claimer address verification and merkle tree verification for claim amount verification, allow for this to work.

Additional Info

I actively worked on this project for around 3 months. My role in the project was to pick up the smart contract in their current state and make any changes needed in order to meet requirements of the product owner. In addition to this I was in charge of writing tests. I wrote more than 200 tests for the smart contract.

At a later point requirements for the project changed and the continuing developer decided to do a complete rewrite of the contracts and the underlying tests.

At the time of writing this it seems that the project lead decided to squash commits at the release which means that none of my commits are shown here. However, my name can be found in the package.json file for anyone curious.

I still do some consulting for the project from time to time when there are certain patterns that need to be checked for security and/or feasability in regards to limitations of solidity and/or gas limits.