French court allows reverse engineering of Skype protocol

An unexpected turn occurred in the case of Microsoft (Skype) against the two owners of the French company Vest Corporation, Christian Durandy and Sean O'Neill. They were accused of distributing the Skype source code.

In 2010, Sean O'Neill published the source code for the obfuscated RC4 key generation algorithm, which Skype uses to obfuscate traffic. With this algorithm, you can decipher the traffic between clients and Skype supernodes. The encryption keys are not used there, so the algorithm itself was obfuscated as much as possible. But, as you know, the principle of security through obscurity often fails, which is what happened in this case.

In general, the history of the company Vest Corporation is rather curious. In 2005, the French government banned the use of Skype for security reasons. In 2007, Durandy and O'Neill decided to establish a company to develop VoIP software that duplicates the functionality of Skype. Deobfuscation and reverse engineering Skype was needed to sort out this program.

In 2011, the Russian hacker Efim Bushmanov ( efimich ) published the source of the Skype protocol on his website skype-open-source.blogspot.com (they are now removed on demand by the DMCA). These sources included a deobfuscated algorithm that O'Neill made public.
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Shortly thereafter, Microsoft decided that it was time to end the lawlessness — and, fortunately, it was not Bushmanov who started the persecution, but French entrepreneurs. A criminal case was initiated against them, which reached the court in September 2013. According to the French press, the prosecutor demanded one year imprisonment for Durandy and O'Neill.

But the French court decided otherwise. The verdict was announced yesterday: all charges were dropped from businessmen, and Microsoft must pay them moral damages in the amount of 1,000 euros.

Thus, the court actually legalized the further reverse engineering of the Skype protocol and the publication of the original algorithms that it uses. It remains to be happy for the French justice, which made a reasonable decision, because in the United States this is hardly possible.