Python Diffie Hellman

Diffie Hellman is a key exchange algorithm that allows two parties to agree on a shared secret key across an insecure communication channel. In Python, we can implement this algorithm using the cryptography library.

Installation

To install cryptography, you can use pip:

pip install cryptography

Implementation

Here's an example implementation of Diffie Hellman in Python:

from cryptography.hazmat.primitives.asymmetric import dh
from cryptography.hazmat.primitives import serialization


# Generate private and public keys for Alice
params = dh.generate_parameters(generator=2, key_size=2048)
alice_private_key = params.generate_private_key()
alice_public_key = alice_private_key.public_key()

# Generate private and public keys for Bob
bob_private_key = params.generate_private_key()
bob_public_key = bob_private_key.public_key()

# Exchange public keys over an insecure channel
alice_shared_key = alice_private_key.exchange(bob_public_key)
bob_shared_key = bob_private_key.exchange(alice_public_key)

# Print the shared secret keys
print("Alice's shared key:", alice_shared_key.hex())
print("Bob's shared key:", bob_shared_key.hex())

The above code generates private and public keys for Alice and Bob, and then exchanges the public keys over an insecure channel. Finally, both parties generate the shared secret key using the exchanged public keys.

Output

The output of the above script will look something like this:

Alice's shared key: 372563320d81f6b227c6ecf71c01af18630f0837eeb028ae2da1da8b57662d79741a61c985ab0b03e9578c656b3487aa3c9d2bf1f463ed792dc880d80cb5936b
Bob's shared key: 372563320d81f6b227c6ecf71c01af18630f0837eeb028ae2da1da8b57662d79741a61c985ab0b03e9578c656b3487aa3c9d2bf1f463ed792dc880d80cb5936b

Explanation

In this example, we're using the dh.generate_parameters() method to generate parameters for the Diffie Hellman algorithm. We're setting the generator value to 2 and the key size to 2048 bits.

Next, we're generating private and public keys for both Alice and Bob using the generate_private_key() method on the parameters object. The public keys are then exchanged over an insecure channel.

Finally, both parties generate the shared secret key using the exchange() method with the exchanged public keys as input.

Conclusion

Diffie Hellman is an important algorithm for secure key exchange, and Python provides a convenient way to implement it using the cryptography library.