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Skype protocol reverse engineered, source available

skype-open-source.blogspot.com

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Re: Skype protocol reverse engineered, source available

#21

Post by barrkel »

michael_dorfman wrote: post #17
_delirium wrote: post #10

Earlier quoted context omitted.

I don't believe it's possible to secure any sort of intellectual-property protection for a mere protocol. The usual way of protecting them, though, is to patent some essential feature needed to implement the protocol, which may or may not be the case here.

Actually, as I've said elsewhere, one easy way of protecting a protocol is to explicitly restrict the right to reverse engineer in in the Terms of Service of the client that implements the protocol. Without that client, there's nothing to reverse engineer.

I'm not sure that's necessarily enforceable everywhere; it can be interpreted as an illegal barrier to competition.

Re: Skype protocol reverse engineered, source available

#22

Post by JoshTriplett »

johkra wrote: post #9
michael_dorfman wrote: post #5

Earlier quoted context omitted.

That still doesn't mitigate the need for lawyers. The protocol is still intellectual property, and reverse engineering it may not be without consequences.

"intellectual property" That's a really muddy term. How exactly can you protect a protocol? Trade secret? Patents? Copyright shouldn't apply if it's a reimplementation. Edit: s/since/if/

While copyright wouldn't apply to an independent reimplementation, the article included links to decompiled versions of the Skype binaries, which would definitely fall under Skype's copyrights. Nothing wrong with using those decompiled binaries to reverse-engineer and document the Skype protocol, and I hope this produces useful results there, but that doesn't make it OK to directly redistribute the decompiled binaries.

Re: Skype protocol reverse engineered, source available

#23

Post by JoshTriplett »

michael_dorfman wrote: post #15
johkra wrote: post #9

Earlier quoted context omitted.

"intellectual property" That's a really muddy term. How exactly can you protect a protocol? Trade secret? Patents? Copyright shouldn't apply if it's a reimplementation. Edit: s/since/if/

The easiest way to is to restrict the right to reverse-engineer in the Terms of Service of the Skype client (which he needs to use, in order to have something to reverse engineer.)

Terms of Service don't necessarily have any legal force, and many jurisdictions have legal protections for the right to reverse-engineer, particularly for interoperability purposes.

Re: Skype protocol reverse engineered, source available

#24

Post by [deleted] »

michael_dorfman wrote: post #15
johkra wrote: post #9

Earlier quoted context omitted.

"intellectual property" That's a really muddy term. How exactly can you protect a protocol? Trade secret? Patents? Copyright shouldn't apply if it's a reimplementation. Edit: s/since/if/

The easiest way to is to restrict the right to reverse-engineer in the Terms of Service of the Skype client (which he needs to use, in order to have something to reverse engineer.)

[deleted]

Re: Skype protocol reverse engineered, source available

#25

Post by JoshTriplett »

Animus7 wrote: post #18

If the goal is to open up Skype, this isn't the way. Even if some insane insomniac de-twiddles the pages upon pages of optimized indirection in this code (which I seriously doubt), all Skype has to do is tweak the protocol or encryption and the researcher is back to square one. It's a losing battle. And that's not even getting into the legality of it it all. How about instead of trying to fruitlessly crack Skype, we…

Both seem quite valuable. Long-term, we want an open peer-to-peer encrypted communication system. Short-term, until Skype dies, it would help to have the ability to interoperate with people who use it. Similarly, while XMPP represents the right open standard for chat, existing Open Source chat programs still need to know how to interoperate with MSN, AIM, and Yahoo

Re: Skype protocol reverse engineered, source available

#26

Post by werg »

Animus7 wrote: post #18

If the goal is to open up Skype, this isn't the way. Even if some insane insomniac de-twiddles the pages upon pages of optimized indirection in this code (which I seriously doubt), all Skype has to do is tweak the protocol or encryption and the researcher is back to square one. It's a losing battle. And that's not even getting into the legality of it it all. How about instead of trying to fruitlessly crack Skype, we…

If the system can successfully masquerade as an older Skype version it stands a chance. That is unless Skype has a baked-in not yet understood mechanism for pushing protocol changes to its clients. Skype would have to find discerning features, implement it on their servers and possibly even push it to their client updates. Whenever such discerning features were found it's a simple matter of arms race, i.e. a difficult but fair chance. Alternatively Skype can start blocking older versions which is rather unlikely.

Concerning the open and better issue; There definitely are open alternatives. None of them have quite the firewall-defying capabilities of Skype. Nor the user base for that matter. Building any kind of social network is fraught with chicken&egg problems and those first to reach mass have it made. Just check how one of the richest and most powerful technology companies Google is struggling to get a foot in Facebook's market.

Re: Skype protocol reverse engineered, source available

#27

Post by braindead_in »

46Bit wrote: post #16
braindead_in wrote: post #12

It seems that the encryption algorithm has been reverse engineered. I guess you'll still need the keys to decrypt the voice data using this algorithm, assuming it works. It's a big deal if has been done, because a lot of people have been trying to crack it. Some governments are going to love this. The Skype client itself has a lot of obfuscation to prevent something like this.

I think it's fair to surmise that those intelligence agencies that care have probably had the algorithm for a long time and searched for weaknesses. Bear in mind that at one time they were complaining about it's use by criminals to avoid phonetaps.

There has been some speculation about a backdoor in Skype which it has shared with intelligence agencies. Never confirmed by Skype of course. But this could allow anyone to decrypt a Skype conversation stream. All you need is a Skype supernode to get started. Or some kind of spyware on the subject's computer which stores/transmits the data stream.

Re: Skype protocol reverse engineered, source available

#28

Post by tttp »

Two major issues: http://skype-open-source.blogspot.com/2011/06/skype-under-rc... || Copyright (c) 2004-2009 by VEST Corporation. || All rights reserved. Strictly Confidential! The project is using existing code, and "All rights reserved" is not an approved OSI license I believe ;)

And things like compression algorithm are patented, and that's very likely skype is using some of it. Reminds me of a project by Intel of providing an implementation of g729 (a voice codec). The source was available, but it was "non commercial usage only" because of the patents mostly.

An interesting project, but doubt we'll see any usable implementation anytime soon IMO. And even if it does, skype will probably alter a bit the protocol to make it fail if it reaches a critical mass.

Re: Skype protocol reverse engineered, source available

#29

Post by gst »

braindead_in wrote: post #27
46Bit wrote: post #16

Earlier quoted context omitted.

I think it's fair to surmise that those intelligence agencies that care have probably had the algorithm for a long time and searched for weaknesses. Bear in mind that at one time they were complaining about it's use by criminals to avoid phonetaps.

There has been some speculation about a backdoor in Skype which it has shared with intelligence agencies. Never confirmed by Skype of course. But this could allow anyone to decrypt a Skype conversation stream. All you need is a Skype supernode to get started. Or some kind of spyware on the subject's computer which stores/transmits the data stream.

If you've got spyware installed on one of the endpoints you don't need any backdoor in Skype. Just dump the audio output and input directly from the audio card.

Re: Skype protocol reverse engineered, source available

#30

Post by jacobr »

Animus7 wrote: post #18

If the goal is to open up Skype, this isn't the way. Even if some insane insomniac de-twiddles the pages upon pages of optimized indirection in this code (which I seriously doubt), all Skype has to do is tweak the protocol or encryption and the researcher is back to square one. It's a losing battle. And that's not even getting into the legality of it it all. How about instead of trying to fruitlessly crack Skype, we…

There is WebRTC (http://sites.google.com/site/webrtc/) for Real Time Communication/Conferencing which Google just open sourced. I think that's the way forward rather than developing a separate "Skype-killer" protocol/app.
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