Proof Of Existence Ethereum Smart Contract

Why

Prove that a document existed at some point.

What

This smart contract stores hash values keyed by a numeric ID on the Ethereum blockchain. Only the contract creator (owner) is allowed to add hashes but anyone can verify a hash.

Prerequisites

Understanding Ethereum and Smart Contracts:

• http://www.lawandblockchain.eu/what-is-ethereum/
• https://medium.com/@preethikasireddy/how-does-ethereum-work-anyway-22d1df506369

Basic understanding of Solidity:

• https://solidity.readthedocs.io/en/latest/introduction-to-smart-contracts.html

Experience with Javascript

Getting Started

1. npm install
2. npx truffle develop starts an in-memory Ethereum blockchain with "immediate mining" ideal for testing and opens a console.
3. npm run test automatically compiles ProofOfExistence.sol, migrates it to your local test chain, and executes ProofOfExistence.spec.js test.

What's Missing

Documentation and configuration to deploy the contract to Ethereum testnets or live.

Help And Further Reading

• Truffle Docs
• https://blog.zeppelin.solutions/the-hitchhikers-guide-to-smart-contracts-in-ethereum-848f08001f05
• truffle-contract is a handy contract abstraction that makes interacting with a contract more convenient than using web3 directly
• Infura is a hosted Ethereum node cluster so you don't have to run your own client/node when deploying to Ethereum's test or live networks. How to configure truffle to use Infura
• Security considerations when coding Smart Contracts with Solidity