For over 10 years, Skype enjoyed selling the world security by obscurity. We must admit, really good obscurity. I mean, really really good obscurity. So good that almost no one has been able to reverse engineer it out of the numerous Skype binaries. Those who could, didn’t dare to publish their code, as it most certainly looked scarier than Frankenstein.
The time has come to reveal this secret. http://cryptolib.com/ciphers/skype contains the greatest secret of Skype communication protocol, the obfuscated Skype RC4 key expansion algorithm
in plain portable C. Enjoy!