[ds]

That heavy lifting wasnt done by myself so I unfortunately dont have a answer for you. This was around a decade ago however, so I would not be surprised if the traffic was unencrypted.

[XMPPwocky]

Source did not encrypt network traffic until DeepBlueSea released NetShark for CS:GO.

Now it uses ICE, a 64-bit block cipher from the DES era. The key is obtained from the Steam servers over the normal Steam encrypted channel.