What I cannot create, I do not understand

• Richard Feynman

A minimal custom blockchain implementation to test my knowledge. Theory is great, but practice is better!

Not a real coin!

Special thanks to Preston Evans for his blockchain implementation and for showing me the Bitcoin world in the first place.

And to Daniel van Flymen for this article showing how to use an API for consensus between nodes.

pipenv shell
pipenv install
python src/server.py <port_number>

Defaults to port 5000. Run with multiple ports at once to see consensus and transactions in action!

• Proof-of-work mining
• Wallet to create transactions, using ECDSA signatures
• Consensus using longest valid chain rule
• Flask API to interact with other nodes (locally, for now)

• Difficulty adjustment
• Coin scarcity
• Smart contract language
• Locktimes
• Block size limit

This was just meant as a challenge for me to make sure

/mine

Mine a new block, returns new block result

/chain

Retrieve blockchain state

/consensus

Find longest valid chain among registered peers. Returns local chain if peers aren't longer or are invalid

/peers/register

Method: POST

Register a new node in local peer list

Example body:

{
  "peers": ["localhost:5005"]
}

/peers/list

Lists peer nodes. These are the nodes the local chain will perform consensus against

/wallet/pubkey

Return the node's associated wallet pubkey and nickname (if applicable)

/wallet/send

Method: POST

Send BLU to another node's wallet

Example body:

{
  "recipient_pubkey": "027b...5024",
  "amount": 20
}

/wallet/balance

Get the wallet's balance (Unverified + Verified)

/wallet/unverified_balance

Get the wallet's balance that's sitting in the mempool

/wallet/verified_balance

Get the balance of the wallet that's confirmed on the blockchain

/mempool

Get the pending transactions for the specified node