Introduction - If you have any usage issues, please Google them yourself
Skype open source code for 1.x/3.x/4.x versions of skype. Including rc4 and arithmetic compression.
** Skype protocol reverse engineered, source available for download **
You have unique chance to take a look on skype internal protocol and encryption. You will see what it uses strong AES and RSA encryption with public key infrastructure.
Autor project files on skype research - Efim Bushmanov