david wong

Hey! I'm David, a security consultant at Cryptography Services, the crypto team of NCC Group . This is my blog about cryptography and security and other related topics that I find interesting.

Diffie-Hellman, ElGamal and RSA

posted April 2014

I'm in holidays for a week, easter I think, anyway, I didn't know what to do so I coded the Diffie-Hellman handshake, the ElGamal cryptosystem and the RSA cryptosystem in python.

You can check the code on github here: github.com/mimoo/crypto_studies

Check the tests.py file to see how the classes are used. Here's an extract:

"""Testing Diffie Hellman
"""
# 1. BOB
bob = DiffieHellman()
# G and g are generated automatically
print("G is a group mod %i and of order %i, and the generator g is %i" % (bob.G[0], bob.G[1], bob.g))
# We generate a secret and a public key
bob.generate_secret()
bob.generate_public()

# 2. ALICE
# We already know G and g
alice = DiffieHellman(bob.G, bob.g)
# We generate the secret key and the public key
alice.generate_secret()
alice.generate_public()

# 3. WE CREATE THE SHARED KEY
bob.generate_sharedkey(alice.publickey)
alice.generate_sharedkey(bob.publickey)
# Bob and Alice now have the same _sharedkey and the same public (G, g)

As the README says, it might be oversimplified and not totally correct. I mostly did that to do something in Python and also try to memorize how those systems work.

I've also done a lot of Unity this week-end. And also a bit of WxPython but I don't really like it. I think I should focus on QT and C++.

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