Simple Blockchain Implementation in Python

This Python script implements a basic blockchain system using the hashlib library for cryptographic hashing and the time module for timestamping. The implementation includes classes for blocks and the blockchain itself, as well as methods to add blocks, validate the chain, and demonstrate tampering detection.

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Table of Contents

1. Overview
2. Key Components
3. How It Works
4. Usage Instructions

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Overview

A blockchain is a distributed ledger technology that allows data to be stored globally on thousands of servers while letting anyone see every transaction that occurs. This implementation provides a simplified version of a blockchain with the following features:

• Blocks: Each block contains an index, timestamp, data, previous hash, and its own hash.
• Blockchain: A collection of blocks linked together via their hashes.
• Validation: Ensures the integrity of the blockchain by checking the consistency of hashes and previous hashes.

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Key Components

1. Block Class

• Represents a single block in the blockchain.
• Attributes:
  • index: Position of the block in the chain.
  • timestamp: Time when the block was created.
  • data: Information stored in the block (e.g., transaction details).
  • previous_hash: Hash of the previous block in the chain.
  • hash: Cryptographic hash of the block's contents.
• Methods:
  • calculate_hash(): Computes the SHA-256 hash of the block's data.
  • __repr__(): Provides a string representation of the block for easy debugging.

2. Blockchain Class

• Represents the entire blockchain.
• Attributes:
  • chain: List of blocks in the blockchain.
• Methods:
  • create_genesis_block(): Creates the first block in the chain (genesis block).
  • add_block(data): Adds a new block with the specified data to the chain.
  • is_chain_valid(): Verifies the integrity of the blockchain by checking hashes and previous hashes.
  • __repr__(): Provides a string representation of the entire blockchain.

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How It Works

1. Initialization:

   • A Blockchain object is initialized with a genesis block, which serves as the starting point of the chain.

2. Adding Blocks:

   • New blocks are created with incremental indices, current timestamps, provided data, and the hash of the previous block.
   • Each block calculates its own hash based on its attributes.

3. Validation:

   • The is_chain_valid() method ensures that:
     • Each block's hash matches the result of recalculating its hash.
     • Each block's previous_hash matches the hash of the preceding block.

4. Tampering Detection:

   • If any block's data or hash is altered, the validation process will detect inconsistencies and flag the blockchain as invalid.

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Usage Instructions

1. Ensure Python 3.x is installed on your system.
2. Save the code to a file, e.g., Min-Block.py.
3. Run the script using the command:

    git clone https://github.com/pi3t4/Mini-Blockchain.git  
   cd Mini-Blockchain
   python Min-Block.py