P2P Blockchain

A peer-to-peer blockchain built from scratch in Rust. This was a learning project to better understand how blockchains work by recreating a P2P network where nodes discover each other, share transactions, mine blocks, and maintain consensus.

Nodes connect over a local network using libp2p, automatically discover peers via mDNS, and broadcast blocks/transactions with Gossipsub. Each node maintains its own copy of the chain, validates incoming blocks, handles forks, and tracks peer reputation.

• Proof-of-work mining with configurable difficulty (BLAKE3 hashing)
• Ed25519 wallets for signing and verifying transactions
• Peer discovery via mDNS — no manual configuration needed
• Gossipsub for broadcasting blocks and transactions
• Request-response protocol for syncing chain state between peers
• Fork handling with cumulative difficulty tracking
• Orphan block pool for out-of-order block arrival
• Peer reputation system that bans nodes sending invalid data
• Interactive CLI for sending coins, mining, and checking status

crates/
├── blockchain-types/   Core types: blocks, transactions, wallets, mining
├── blockchain/         Chain management, fork handling, orphan pool
├── mempool/            Pending transaction queue
├── network/            libp2p networking (Gossipsub + mDNS + request-response)
├── node/               Orchestrates blockchain, network, mempool, and sync
└── cli/                Interactive terminal interface

• Rust (nightly toolchain — automatically selected via rust-toolchain.toml)

cargo build --release

# Generate a random wallet
cargo run --release -p cli

# Or provide a seed for a deterministic wallet
cargo run --release -p cli -- myseed

To run multiple nodes on the same machine, open separate terminals and run the command in each — they will discover each other automatically.

Logs are written to blockchain.log. Use tail -f blockchain.log in another terminal to watch activity.