5.6.23Trustplatform9.17a.txt

import random
import hashlib

# Returns a new private key
def generate_private_key():
    return random.randint(1, 65535)

# Returns the public key corresponding to the given private key
def generate_public_key(private_key):
    # Perform a hash of the private key and convert the result to an integer
    hashed_key = int(hashlib.sha256(str(private_key).encode('utf-8')).hexdigest(), 16)
    
    # Use the hashed key as the public key
    return hashed_key

# Generates a new keypair and adds it to the trust network
def generate_keypair(trust_network):
    private_key = generate_private_key()
    public_key = generate_public_key(private_key)
    trust_network[public_key] = set()
    return private_key, public_key

# Sends a message from the sender to the recipient
def send_message(sender_private_key, sender_public_key, recipient_public_key, trust_network, message):
    # Encrypt the message using the recipient's public key
    encrypted_message = pow(message, recipient_public_key, recipient_public_key)
    
    # Sign the encrypted message using the sender's private key
    signature = pow(encrypted_message, sender_private_key, sender_public_key)
    
    # Add the recipient's public key to the set of trusted keys for the sender's public key
    trust_network[sender_public_key].add(recipient_public_key)
    
    # Return the encrypted message and signature
    return encrypted_message, signature

# Receives a message from the sender
def receive_message(sender_public_key, recipient_private_key, trust_network, encrypted_message, signature):
    # Verify that the sender's public key is trusted by the recipient's private key
    if sender_public_key not in trust_network[recipient_private_key]:
        raise Exception("Sender's public key is not trusted.")
    
    # Verify the signature using the sender's public key
    if pow(signature, sender_public_key, sender_public_key) != pow(encrypted_message, recipient_private_key, sender_public_key):
        raise Exception("Invalid signature.")
    
    # Decrypt the message using the recipient's private key
    message = pow(encrypted_message, recipient_private_key, sender_public_key)
    
    # Return the message
    return message

# Initializes the trust network with a set of trusted public keys
def initialize_trust_network(trusted_public_keys):
    trust_network = {}
    for public_key in trusted_public_keys:
        trust_network[public_key] = set(trusted_public_keys)
    return trust_network

# Example usage
if __name__ == '__main__':
    # Initialize the trust network with a set of trusted public keys
    trusted_public_keys = [generate_public_key(12345), generate_public_key(67890)]
    trust_network = initialize_trust_network(trusted_public_keys)
    
    # Generate a new keypair and add it to the trust network
    alice_private_key, alice_public_key = generate_keypair(trust_network)
    
    # Generate a new keypair and add it to the trust network
    bob_private_key, bob_public_key = generate_keypair(trust_network)
    
    # Alice sends a message to Bob
    message = 123
    encrypted_message, signature = send_message(alice_private_key, alice_public_key, bob_public_key, trust_network, message)
    
    # Bob receives the message from Alice
    received_message = receive_message(alice_public_key, bob_private_key, trust_network, encrypted_message, signature)
    print("Bob received message:", received_message)
    
    # Try to receive a message

def receive_message(sender_public_key, receiver_private_key, trust_network, encrypted_message, signature):
    # Verify the signature with the sender's public key
    if verify_signature(encrypted_message, sender_public_key, signature):
        # Decrypt the message with the receiver's private key
        decrypted_message = decrypt_message(encrypted_message, receiver_private_key)
        # Check if the sender is trusted by the receiver
        if sender_public_key in trust_network[receiver_private_key]:
            return decrypted_message
        else:
            print("Sender is not trusted.")
    else:
        print("Invalid signature.")

def main():
    # Set up the trust network
    trust_network = {}
    alice_key = generate_keys()
    bob_key = generate_keys()
    trust_network[alice_key[1]] = [alice_key[0], bob_key[0]]
    trust_network[bob_key[1]] = [bob_key[0]]
    
    # Alice sends message to Bob
    alice_message = "Hello Bob!"
    encrypted_message, signature = send_message(alice_key, bob_key[0], alice_message)
    
    # Bob receives the message from Alice
    received_message = receive_message(alice_key[0], bob_key, trust_network, encrypted_message, signature)
    print("Bob received message:", received_message)
    
    # Try to receive a message from an untrusted sender
    eve_key = generate_keys()
    eve_message = "I am an attacker!"
    encrypted_message, signature = send_message(eve_key, bob_key[0], eve_message)
    received_message = receive_message(eve_key[0], bob_key, trust_network, encrypted_message, signature)
    print("Bob received message:", received_message)
    
if __name__ == "__main__":
    main()