Blockchain

This project is a simple implementation of a Blockchain, managed by a group of miners. Blockchain is a tecnology that "guarantees" the order of a given set of events. If these events are bank transactions, it "solves" the double spending problem. Another important element of these systems is Digital Signature, which guarantees authentication, non-repudiation, and integrity.

Routine:

• Data (digitally signed) is sent to the Unconfirmed Data (a FIFO queue);
• A miner takes an unconfirmed data entry;
• Miner solves a "Proof of Work" problem, in this project a simple Left(Hash(block, nonce), 3) < 100. Function used for Bitcoin takes around ~10 minutes/block to find a correct value for nonce property;
• Miner broadcasts block;
• Other miners receive the block, confirm the integrity of the block (hash validation), and add it to their Blockchain;
• If the block is not validated (hash), miners won't add it to their Blockchain and won't broadcast it;
• In case of forks in the chain, the longest chain should be kept, and the other blocks sent back to the Unconfirmed Data.

Main classes:

• Block, only has properties;
• Blockchain, list of blocks;
• BlockFactory, class that generates blocks;
• HashEstimator, responsible for hash estimation;
• UnconfirmedDataFifo, FIFO queue, with the unconfirmed data;
• Miner, responsible for getting data, solving blocks, and broadcasting them.