[phyrrus9]

AES seems kind of stupid for a communications protocol. You have to transmit the key at some point, which automatically defeats the encryption. public-key crypto best fits this sort of thing.

Usually you use public key to transfer the symmetric key for the encryption of messages like in SSL. Asymmetric keys are not designed to be used for constant encryption and decryption due to their poor performance in speed.

It's nothing about design and all about security. If you've got to use public key encryption in the first place why not just use public key encryption for the whole system. I find many python programmers tend to overlook these things