Cryptography Term Project Assignment 2

Group 16 Details

Name	ID
Rakul Chauhan	2021AAPS1971H
Atharva Chikhale	2021A7PS2752H
Shubham Gupta	2021A8PS2953H
Manas Jalan	2020B4A70678H
Pratyush Tripathi	2020B3AA1838H

Contract Management System

This project aims to develop a system for Contract Management with verification using HMAC(Hash-based Message Authentication Code).

Technology Used:

• Python

Contents

• Introduction
• How to Use
• main.py file
• Classes(Files)
• Class_Functions
• Steps to Run the Code
• Usage Example

Introduction

This system consists of three main classes: CONTRACT, BLOCK, and BLOCKCHAIN.

• CONTRACT represents a contract, storing its ID, amount, issuer ID, and user ID. It also handles key generation, challenge creation, HMAC creation, and verification.
• BLOCK represents a block in the blockchain, containing a list of transactions, index, timestamp, and previous block's hash.
• BLOCKCHAIN manages the blockchain, including creating blocks, adding transactions, verifying transactions, and ensuring the validity of the blockchain.

How to Use

1. Creating Contracts: Users can create contracts by providing contract ID, amount, issuer ID, and user ID. The system automatically generates a private key for each contract.
2. Adding Transactions: Users can add transactions to the blockchain, verifying them using HMAC. Each block can contain up to a specified number of transactions (TRANSACTION_LIMIT).
3. Verification: Users can verify transactions against their respective contracts using HMAC.
4. Viewing Data: Users can print the entire blockchain, view transactions of a specific user, check the total number of contracts, and see the total number of unique users.
5. Checking Validity: Users can check if the blockchain is valid.

main.py file

Functions:

• main(): The main function of the program which controls the flow of execution.
• BLOCKCHAIN(diff): A constructor for the BLOCKCHAIN class which initializes the blockchain with the specified parameter.
• verifyTransaction(tx, contract_id, user_id, issuer_id, amount): Verifies if a transaction is valid.
• addTransaction(tx): Adds a new transaction to the blockchain.
• printChain(): Prints the entire blockchain.
• viewUser(user_id): Prints all transactions related to a specific user.
• getNoOfContracts(): Prints the total no. of contracts and the sum of amounts across all these contracts.
• getTotalUsers(): Prints the total number of unique users.
• isChainValid(): Checks if the blockchain is valid.

Variables:

• diff : Difficulty used for mining blocks.
• count: The number of transactions the user wants to add to the blockchain.
• i: A counter variable used in the for loop for adding transactions.
• tx: A vector of CONTRACT objects representing the transactions added to the blockchain.
• contract_id : Unique ID for a contract(string).
• amount: The amount of money being transferred in a contract(double).
• issuer_id: An identifier for every issuer of a contract(string).
• user_id: An identifier for every user in the blockchain(string).
• tx_temp: A CONTRACT object used to store a transaction before it is added to the blockchain.
• control: An integer variable used to control the switch case in the program.

Classes(Files)

1. CONTRACT: Represents a contract and provides methods for key generation, challenge creation, HMAC creation, and verification.
2. BLOCK: Represents a block in the blockchain and calculates its hash.
3. BLOCKCHAIN: Manages the blockchain, creates blocks, adds transactions, verifies transactions, and ensures blockchain validity.

Class_Functions

CONTRACT

• __init__(self, c_id, amt, i_id, u_id): Constructor method for the CONTRACT class.
• make_key(self, c_id, amt, i_id, u_id): Generates a private key for a contract.
• generate_challenge(self): Generates a challenge for a transaction.
• set_rand_bit(self, bit): Sets a random bit for a transaction.
• create_hmac(self): Creates HMAC for a transaction.
• doSomeHash(self, data): Performs hashing for key generation.

BLOCK

• __init__(self, idx, prevHash): Constructor method for the BLOCK class.
• calculateHash(self): Calculates hash for a block.

BLOCKCHAIN

• __init__(self, diff): Constructor method for the BLOCKCHAIN class.
• getNoOfContracts(self): Prints the total number of contracts present.
• getTotalUsers(self): Prints the total number of unique users.
• generate_basic_hash(self, data): Generates a basic hash for blockchain.
• calculateHash(self, block): Calculates hash for a block.
• mineBlock(self, newBlock, difficulty): Mines a block with a specified difficulty.
• createBlock(self): Creates a new block if the current block reaches the transaction limit.
• addTransaction(self, tx): Adds a transaction to the blockchain.
• verifyTransaction(self, tx, c_id, u_id, i_id, amount): Verifies a transaction using HMAC.
• isChainValid(self): Checks if the blockchain is valid.
• viewUser(self, user_id): Views transactions of a specific user.
• printChain(self): Prints the entire blockchain.

Steps to Run the Code

1. Ensure you have Python installed on your system.
2. Download the provided Python files to your local machine.
3. Open a terminal or command prompt and navigate to the directory where the files are located.
4. Run the main.py file by executing the command: python main.py.
5. Follow the on-screen instructions to interact with the program.

Usage Example

# Example usage
blockchain = BLOCKCHAIN(4)  # Initialize blockchain with difficulty 4

# Add transactions to the blockchain
contract_id = "1"
amount = 100.0
issuer_ID = "abc12"
user_id = "xyz24"