G Coin

A simple implementation of Blockchain for understanding easily.

It includes only basic concepts.

• Block and Hash
• Transaction and Balance
• Mining with Proof of Work
• Chain validation and consensus conflicts

Articles (Korean)

※ 아래 글은 최신 버전의 코드가 반영되어 있지 않습니다. 참고해주세요.

• 골빈해커님의 g-coin 분석 1부
• 골빈해커님의 g-coin 분석 2부
• 골빈해커님의 g-coin 분석 3부 (Comming soon)

Modules

bold is core function.

• blockchain : chain structure /w blocks
  • new_block: make block /w hash of previous block and current proof
  • valid: validate chain rules of all chain
• block : block structure
  • hash: hash itself
• proof : proof of work
  • find_proof
  • valid_proof
• miner : Mining new block and get rewards
• transaction : data object
• book : book of transactions
  • check_balance /w transaction history of sender account
• node
  • consensus_with_neighbor

Endpoints

• /transaction : Add a transaction and get pending transactions.
• /mine : Mining. Find proof and make block with rewards.
• /node : Add a node as a neighbor node
• /chain : Get full chain to validate.
• /chain/valid : Valid chain
• /chain/consensus : Consensus conflicts

Basic Flow

• /transaction: Add trasaction for sending coin.
  • Check balance and add to blockchain
  • Use '0' as a sender id at the first time. It's the genesis wallet.
• /mine: Mining for making block.
  • Find proof with previous proof
  • Add a reward to transactions
  • Make a new block with proof and hash of previous block
  • Add the block to chain of blocks
  • Clear current transactions
• /chain/consensus: Consensus conflicts with neighbor nodes.
  • Fetch blockchain from all neighbor nodes.
  • Check which has the longest chain and valiates it's chain.
  • Add neighbor nodes before do this using /node

Try using Insomnia

• Download Insomnia
• Import from insomnia.json

Mining practice

python app.py --port 5000

• First try
  • POST /transaction
    • /w {sender: '0', recipient: 'golbin', amount: 10}
  • GET /transaction
  • GET /chain
  • POST /mine
  • GET /chain
  • GET /transaction
• Second try
  • POST /transaction
    • /w {sender: 'golbin', recipient: 'bluecat', amount: 10}
  • POST /transaction
    • /w {sender: 'golbin', recipient: 'bluecat', amount: 10}
  • POST /mine
  • GET /chain

Consensus practice

python app.py --port 5000
python app.py --port 5001

• POST /node
  • to 127.0.0.1:5000 /w {address: '127.0.0.1:5001'}
• POST /node
  • to 127.0.0.1: 5001 /w {address: '127.0.0.1:5000'}
• Try several mining
• GET /chain/valid
• POST /chain/consensus

Requirements

• Python >= 3.6
• Flask >= 0.12
• Requests >= 2.18

TODO

• Merkle root implementation
• Check balance in transactions in next blocks
• Fix balance of genesis account
• Broadcast transactions
• Use DB

References

• http://ecomunsing.com/build-your-own-blockchain
• https://hackernoon.com/learn-blockchains-by-building-one-117428612f46