🧱 Simple Blockchain with Proof of Work and CLI in Go

This is a minimal blockchain implementation written in Go. It demonstrates how a basic blockchain works by chaining blocks together using cryptographic hashes and includes a simple Proof-of-Work (PoW) mechanism for mining new blocks. It uses BoltDB for persistent storage and provides a basic command-line interface (CLI) for interacting with the blockchain.

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🔧 Features

• ✅ Creates a genesis block
• ✅ Adds new blocks to a persistent chain
• ✅ CLI to interact with the chain
• ✅ Each block includes:
  • Data (e.g. transactions)
  • Hash of the previous block
  • Its own SHA-256 hash (simplified)
  • Nonce (for PoW)
• ✅ Implements Proof-of-Work:
  • Adjustable difficulty via targetBits
  • Mines blocks by finding a valid nonce
  • Validates PoW on each block
• ✅ Uses BoltDB for local data storage
• ✅ Added support for transactions and transaction rewards
• ✅ Added wallet functionality with public/private key pairs
• ✅ Network Support:
  • Starts a TCP server node
  • Nodes can send and receive blocks and transactions
  • Handles new block propagation across the network
  • Includes basic peer-to-peer functionality

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🧠 How It Works

Each block contains data and references the previous block's hash. A SHA-256 hash is computed from the block's data, previous hash, and a nonce. The Proof-of-Work algorithm ensures the block hash is below a target value, enforcing difficulty and securing the blockchain.

The blockchain now supports transactions, where each block may contain one or more transactions. Each wallet generates public/private keys and is used to manage transactions and block mining. A peer-to-peer network allows nodes to communicate, propagate new blocks and transactions, and maintain consensus.

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📦 Getting Started

✅ Prerequisites

Make sure you have Go installed:
👉 https://golang.org/dl/

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🏃 Run the Program

Clone the repository:

git clone https://github.com/loid-lab/blockchain.git
cd blockchain
go run main.go

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🧪 CLI Usage

Command	Description
addblock -data=X	Adds a block with transaction data
createwallet	Creates a new wallet (public/private key pair)
miningreward	Creates a mining reward transaction (coinbase)
printchain	Prints all blocks in the blockchain

Example

go run main.go addblock -data="Send 1 BTC to Ivan"
go run main.go addblock -data="Send 2 more BTC to Ivan"
go run main.go printchain

Sample Output

Prev. hash: 
Data: Genesis
Hash: abc123...

Prev. hash: abc123...
Data: Send 1 BTC to Ivan
Hash: def456...

Prev. hash: def456...
Data: Send 2 more BTC to Ivan
Hash: ghi789...

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📝 Notes

This is a learning and demo project. It does not include:

• Real cryptographic hash functions or difficulty adjustments
• Full consensus or network security (basic P2P is included)
• Wallets or real transactions
• Security, encryption, or signatures

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📚 Resources

• 📘 Mastering Bitcoin – Andreas M. Antonopoulos
• 📘 Go Programming Language
• 📘 BoltDB

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📄 License

This project is licensed under the MIT License.
Feel free to fork and improve!