Simple Decentralized Blockchain

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Overview

This project implements a basic blockchain system featuring:

• Transaction management
• Proof of Work (PoW) mining
• Blockchain validation and integrity check
• Node registration and consensus resolution for decentralization

Built with Python and Flask, and tested via PowerShell automation scripts.

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Features

• Add and manage transactions
• Mine blocks with Proof of Work
• Validate blockchain integrity
• Register multiple nodes
• Reach consensus across nodes (longest valid chain rule)

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Execution

1️. Start the Python Blockchain Node(s)

Run the Python server(s):

python blockchain.py -p 5000 --node-id node_A

2. Start more nodes for testing decentralization:

python blockchain.py -p 5001 --node-id node_B

python blockchain.py -p 5002 --node-id node_C

3. Run the PowerShell Script

Test local blockchain

After the servers are running, execute the automation script:

.\run_blockchain.ps1

Test decentralization & consensus

For decentralization and consensus testing:

.\test_blockchain.ps1

These scripts automatically:

• Add and broadcast transactions between nodes
• Mine new blocks using Proof of Work
• Display blockchain content after each block is mined
• Resolve conflicts and synchronize nodes through consensus
• Validate the integrity of all chains

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Results

Local Test (run_blockchain.ps1)

• Blockchain starts with the genesis block (Index 0)
• New transactions are added (e.g., Alice → Bob, Bob → Charlie)
• Each block mined includes the miner reward (Network → node_A: 1)
• Final blockchain shows all blocks correctly linked and validated

Example Output:

Index: 0, Hash: 0000a3f...
Transactions: []

Index: 1, Hash: 000056b...
Transactions: Alice → Bob, Network → node_A: 1

Blockchain valid: True

Decentralization Test (test_blockchain.ps1)

• Three nodes (5000, 5001, 5002) start independently
• Each node mines different blocks → conflict occurs
• Consensus algorithm is triggered → all nodes adopt the longest valid chain
• Synchronization complete: every node has the same blocks

Final Output:

Node 5000 -> Blocks: 4 | Valid: True
Node 5001 -> Blocks: 4 | Valid: True
Node 5002 -> Blocks: 4 | Valid: True

Decentralization test successful: All nodes are synchronized and the blockchain integrity is verified