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Blockendance is a complete blockchain implementation built from scratch in Python, demonstrating core blockchain concepts through a practical attendance management system. This project showcases how to build a functional blockchain without relying on existing blockchain frameworks.

• Pure Python Implementation: Every component built from scratch
• Complete Blockchain Architecture: Genesis block, block creation, chain validation
• Cryptographic Security: SHA-256 hashing and block linking
• Real-world Application: Practical attendance management use case
• Educational Value: Perfect for understanding blockchain fundamentals

classBlock:-index:Blockpositioninchain-timestamp:Blockcreationtime-data:Attendancerecords (JSON)-prev_hash:Previousblock'shash-hash:Currentblock'sSHA-256hash

• First block in the chain (index 0)
• No previous hash reference
• Initializes the blockchain

• Cryptographic hash verification
• Block linkage integrity
• Tamper detection algorithms

• Once written, data cannot be modified
• Any tampering breaks the chain
• Cryptographic proof of integrity

Blockendance/├── block.py           # Block class with hashing and validation├── genesis.py         # Genesis block creation├── newBlock.py        # New block creation and addition├── getBlock.py        # Block retrieval and search├── checkChain.py      # Blockchain integrity verification├── blockchain.py      # Main Flask application└── templates/         # Web interface templates

• SHA-256 Hashing: Each block secured with cryptographic hash
• Chain Linking: Blocks linked via previous block hashes
• Tamper Detection: Any modification breaks the chain
• Data Integrity: Immutable record storage

• Block Creation: Automated block generation with proper indexing
• Chain Validation: Complete integrity checking algorithms
• Data Retrieval: Efficient search through blockchain
• Statistics: Real-time blockchain analytics

• Responsive Design: Modern Material Design UI
• Form Validation: Client and server-side validation
• Real-time Feedback: Live attendance counting
• Error Handling: Comprehensive error management

• Python 3.6 or higher
• pip package manager

1. Clone the repository

git clone https://github.com/adeen-s/Blockendance.gitcd Blockendance

2. Install dependencies

pip install Flask

3. Run the application

python blockchain.py

4. Access the applicationOpen your browser and navigate tohttp://localhost:5001

defcreate_genesis_block():genesis_data= {"type":"genesis","message":"Genesis Block - Blockchain Initialized","creator":"Blockendance System"    }returnBlock(0,datetime.now(),genesis_data,"0")

defnext_block(last_block,data):this_index=last_block.index+1this_timestamp=datetime.now()this_data=copy.deepcopy(data)this_prev_hash=last_block.hashreturnBlock(this_index,this_timestamp,this_data,this_prev_hash)

defcheck_integrity(chain):fori,blockinenumerate(chain):ifnotblock.is_valid():returnf"Error: Block #{i} has invalid hash"ifi>0andblock.prev_hash!=chain[i-1].hash:returnf"Error: Block #{i} not properly linked"return"Blockchain integrity verified"

This project demonstrates:

• Blockchain Fundamentals: Core concepts without complexity
• Cryptographic Hashing: SHA-256 implementation
• Data Structures: Linked list of blocks
• Web Development: Flask framework integration
• Security Principles: Immutability and integrity

• Educational: Learn blockchain development
• Proof of Concept: Demonstrate blockchain applications
• Research: Study blockchain behavior
• Development: Base for larger blockchain projects

• Educational Purpose: This is a simplified blockchain for learning
• No Consensus: Single-node implementation (no mining/proof-of-work)
• Centralized: Runs on single Flask server
• No Persistence: Data lost on restart (can be extended)

Contributions are welcome! Please feel free to submit a Pull Request.

This project is licensed under the MIT License - see theLICENSE file for details.

Adeen Shukla -Initial work -GitHub

Built with ❤️ to demonstrate blockchain technology from scratch