PyDHE is an instructional implementation of the Diffie-Hellman key exchange protocol in Python. A background tutorial can be found at http://blog.markloiseau.com/2013/01/diffie-hellman-tutorial-in-python/.

DiffieHellman.py contains a functional implementation of the protocol, and SimpleDHE.py includes a simplified example of the protocol's steps.

PyDHE is provided as a demonstration of the Diffie-Hellman key exchange protocol. Per the GPL, it is provided without any warranty or implication of fitness for a purpose.

WARNING: The code in this project is for instructional purposes only. No matter how smart you might think you are, it's unwise to use homebrew encryption code in sensitive or production environments. Never use the following code in a production environment, either. If you need real security, use an established, audited and thoroughly tested encryption package like OpenSSL or GNUTLS.

The following code performs a complete exchange, including key generation using SHA-256:

a = DiffieHellman()
b = DiffieHellman()

a.genKey(b.publicKey)
b.genKey(a.publicKey)

if(a.getKey() == b.getKey()):
	print "Shared keys match."
	print "Key:", hexlify(a.key)

The DiffieHellman class uses parameters recommended by RFC 3562 for generation of a 256-bit key, including a 6144-bit MODP prime and an exponent that is at least 540 bits in length.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.