RSA with PyCrypto

[Tommy Lindgren]

Hi!

I am writing a P2P instant messenger and I would to like to encrypt
the messages using a symmetric crypto (DES3) and encrypt the DES3-key with
an asymmetric crypto (RSA). PyCrypto seems nice for this task, but I don't
understand how the RSA instances are supposed to exchange public keys.

An example:

from Crypto.PublicKey import RSA
from Crypto.Util.randpool import RandomPool
rpool = RandomPool()

# Generate keys
privkeyA = RSA.generate(368, rpool.get_bytes)
privkeyB = RSA.generate(368, rpool.get_bytes)
pubkeyA = privkeyA.publickey()
pubkeyB = privkeyB.publickey()

# Give B's public key to A... I think...
privkeyA.e = pubkeyB.e
privkeyA.n = pubkeyB.n

# A can now encrypt messages for B, as long as I don't give A's public key
# to B (which feels strange, but I am not too knowledgeable about the
# RSA algorithm)

msg = 'Follow the white rabbit.'
msgc = privkeyA.encrypt(msg, '')
msgd = privkeyB.decrypt(msgc)


So, is there a better way to exchange public keys?

TIA
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