Skype protocol reverse engineered, source posted online

By on June 3, 2011, 3:05 PM

Efim Bushmanov has decided he wants to open source the Skype protocol. The researcher claims to have already achieved the reverse engineering part.

Bushmanov has posted,, and on He has also uploaded a torrent file to The Pirate Bay and posted the source on GitHub. The source code encompasses Skype versions 1.x, 3.x, and 4.x as well as details of the rc4 layer arithmetic encoding the service uses.

"While 'Wall Street Journal' makes politics and Skype today's trend, I want to publish my research on this," Bushmanov writes in a statement. "My aim is to make Skype open source. And find friends who can spend many hours for completely reverse it."

The code available for download will give insight into how Skype works. On the other hand, this could result in multiple security risks for Skype if holes are found that can be exploited.

"This unauthorized use of our application for malicious activities like spamming/phishing infringes on Skype’s intellectual property," a Skype spokespersons said in a statement. "We are taking all necessary steps to prevent/defeat nefarious attempts to subvert Skype’s experience. Skype takes its users’ safety and security seriously and we work tirelessly to ensure each individual has the best possible experience."

Following rumors that Google, Facebook, and Microsoft were all interested in the Skype, the software giant swooped in. Last month, Microsoft announced that it was acquiring Skype for $8.5 billion in cash. The deal was approved by the boards of directors of both companies, and is Microsoft's largest acquisition to date.

It will be quite difficult for Bushmanov to try to open source Skype with the VoIP company breathing down his back. It will be even more difficult to do so with the largest software company in the world trying to stop him. Microsoft will make sure that Skype will remain a closed platform. We'd be surprised if Redmond allowed this to get very far, assuming that Skype itself doesn't shut down the efforts before the acquisition is completed.

Even if there were no legal obstacles to surmount, I honestly don't see the point of trying to open source Skype. The service is excellent the way it is, and there are many alternatives available anyway.

User Comments: 8

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Guest said:

Closed IM/VoIP systems are stupid anyway, and it's a shame they ever got a foothold rather than an open or otherwise interoperable protocol. Imagine if the telephony system or emails were a bunch of closed and competing platforms rather than a set of standards, i.e. you could only use Gmail to contact other Gmail users, if you wanted to email someone with a Hotmail email address you'd have to sign up for hotmail. It's ridiculous and anti-consumer.

Guest said:

"Closed IM/VoIP systems are stupid anyway,"

Problem is it's hard to get everyone to standardize on this when there are so many competing standards since beginning of time. trying to standardize VOIP is like trying to standardize IM and also create a single Linux distro/repository. Just ain't gonna happen. At least Skype is the closest thing to a "standard", in that it has the most users and works on many platforms.

Guest said:

"Efim Bushmanov has decided he wants to open source the Skype protocol"

I can't wait to see what kind of (legal) trouble this is gonna cause for Efim. You can bet the lawyers are licking their chops. Besides, rather than work on someone else's work, why not try and make GNU free call better? This is like Linux focusing on using "wine" to run windows programs rather than just running NATIVE Linux programs.

Guest said:

@ Guest2

Yes, which is why it's a shame Microsoft has bought Skype rather than someone like Google, who may have had the decent to open it up and let people build third party clients (Google Talk uses XMPP which is an attempt at a standarised and open IM protocol, and Google Wave was intended to become an open standard also).

At best Microsoft will keep Skype as it is and hopefully make it interoperable with, or as a replacement to WLM. At worst they could drop or sideline support for non Microsoft platforms, although I suspect they won't due to fear of the backlash that would cause.

SuzanneL said:

I indeed do remember the days when Compuserve customers could only "email" Compuserve customers, and although I had internet at work, my mother thought it was I who was constrained from emailing her, not the other way around. Oh so clever Compuserve (and later AOL) thought it was leverage to keep their customers corralled to each other, but are either of those names even relevant anymore? I knew it was the internet that was going to win that one, but it was impossible to my family explain at the time.

Anyway, I don't know why Efim Bushmanov did what he did, because there are already open source VOIP softwares available - - but the really nice things Skype has going for it that Microsoft wants is a) it's closed source, b) it has a very nice intuitive interface, and c) it's already ported to Linux. If Microsoft does not retain a toe hold in some aspect of the Linux market, it will be sunk long term. As more people save money by repairing their old computers with the now very slick Ubuntu Linux, rather than buy new Windows computers, look for some very nasty leverage points MS-Skype will try to use against Linux. Because that's how MS does business.

What one of these existing open source VOIPs need is a corporate sponsor, the way Oracle put a big dent in MSOffice by sponsoring OpenOffice. Maybe Yahoo would be a good candidate to leverage against MS-Skype by releasing it's own nice VOIP Yahoo Instant Messenger as open source.

Guest said:

Bah he did not post the torrent himself. All it takes is to read the comments in his blog! He is likely to have posted it only on one source, and other users propagated it.

Guest said:

I can name one good reason to open source skype:

While the Mac and Windows versions of skype are awesome, the linux version is -terrible-. Just. TERRIBLE. I always keep more than one copy of it open at any given time because it frequently crashes and has problems with my sound drivers.

Not to mention, even if it did work correctly, the linux skype version is over three versions old. It does not interact well with the current skype on other platforms.

I really hate skype. It's so proprietary and the only version I can use is so darned buggy. It wouldn't be so bad if everyone didn't use skype, but they do.

Archean Archean, TechSpot Paladin, said:

the way Oracle put a big dent in MSOffice by sponsoring OpenOffice.

I am not sure about this statement as MS office still has a strangle hold, and TBH having used so many flavors of open office, I was impressed with none, they are ok for a basic user, but not for a power user, period. Secondly, in corporate sector they don't want to experiment with every new incarnation of something just because it is free (read open source).

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