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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

#51

Post by jcr »

lesterbuck wrote: post #48
jcr wrote: post #39

Earlier quoted context omitted.

Actually, no. If you look at those files, you're "tainted" and can't be the one who writes a new implementation. The correct way to do reverse engineering for compatibility is to have to completely separate teams. The first does the reverse engineering and writes the specification/documentation. The second completely separate teams takes the specs/docs and writes an entirely new implementation. This is the process us…

Of course that was not the way the "IBM PC Compatible" market arose. IBM published a rather complete set of documentation of the system, including all interface signals and the BIOS source code. I still have several of those documents on my shelf. It is completely different from the complete lack of Skype technical documents.

IBM released documentation after the PC had been cloned through "clean room" reverse engineering.

http://en.wikipedia.org/wiki/IBM_PC_compatible

Re: Skype protocol reverse engineered, source available

#52

Post by daeken »

zerd wrote: post #38
yread wrote: post #11

with identifiers like unpack_41_715680 and the_thing it is not exactly easy to read

That's life for reverse engineered stuff. If you don't really know what a function does, how do you name it?

You come up with a name based on the observed behavior. I'm honestly amazed that they've made it as far as they have without decent naming conventions -- the use of good identifiers in your IDBs cuts reversing time way, way down.

Re: Skype protocol reverse engineered, source available

#54

Post by VMG »

jcr wrote: post #44

I wouldn't venture to say this doesn't belong on HN since it really is interesting (if it was actually done correctly), but the files available for download are most likely illegal, were most likely created with pirated tools (IDA Pro/Hex-Rays, and yes, as a customer of theirs for over a dozen years I've reported it), and of course, the usual vilification of reverse engineering. If you're reading this on a desktop or…

Why do you assume the tools are pirated?

Re: Skype protocol reverse engineered, source available

#55

Post by 46Bit »

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.

Quite possibly, and certainly I think they could get it if they really wanted. Certainly it can't be much worse that typical public email providers where law enforcement seem to pretty much just have to type an email into a form to browse your inbox.

Re: Skype protocol reverse engineered, source available

#56

Post by braindead_in »

gst wrote: post #29
braindead_in wrote: post #27

Earlier quoted context omitted.

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.

Easier said then done. The most reliable way to dump audio output is by API Hooking, which isn't easy in the first place and detectable by AV, Spybot etc. It much simpler to intercept the network traffic.

Re: Skype protocol reverse engineered, source available

#58

Post by peterwwillis »

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…

> How about instead of trying to fruitlessly crack Skype, we spend the time making something that's both open and better?

There's value in making an open client that works with the existing network (for example, Microsoft recently killed the Skype integration plug-in for Asterix).

Re: Skype protocol reverse engineered, source available

#59

Post by lurker19 »

michael_dorfman wrote: post #31
barrkel wrote: post #21

Earlier quoted context omitted.

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

That might be true; but do you want to be responsible for hiring the team of lawyers to go head-to-head against Microsoft's lawyers on that point?

Thanks for reminder to contribute to the EFF this year.

We have strength in numbers.

Re: Skype protocol reverse engineered, source available

#60

Post by crocowhile »

michael_dorfman wrote: post #19
crocowhile wrote: post #13

Earlier quoted context omitted.

Can you say more?

A simple Google search turns up this: http://www.hex-rays.com/decompiler.shtml

yes, I saw that. I just cannot believe that this is simply the digested work of a (yet special) decompiler.
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