Skype Reverse Engineered?

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Tom Keating
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Skype Reverse Engineered?

According to TechCrunch, someone named Sean O'Neill is claiming he reverse-engineered Skype, laying bare one of the most closely guarded secrets in VoIP Land. Has Skype's Great Wall of VoIP been cracked? Skype takes protection of their proprietary protocol very seriously. Need I remind you of the various JoltID lawsuits by Skype co-founders Niklas Zennstrom and Janus Friis which owns the Skype's P2P "secret sauce"?

If indeed Skype has been cracked, this could have major implications, including not just security, but also some beneficial effects, such as 3rd parties embedding Skype more easily into their products and bypassing Skype's relatively new Skype API called SkypeKit SDK.

Sean writes on his blog:

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. contains the greatest secret of Skype communication protocol, the obfuscated Skype RC4 key expansion algorithm in plain portable C. Enjoy!

He ends the blog entry with a "teaser" to "come to Berlin for 27C3 to hear all the juicy details on how to use this function to decrypt Skype traffic. With best regards, Skype Reverse Engineering Team".

Hoax? Legit?

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