Skype 5-way Calling Limit Cracked

BobPaul writes "It turns out when Skype limited 10 way calling to Intel Processors only it really was arbitrary! Maxxus has a patched version of Skype that allows 10-way calling regardless of the processor installed. There's also info about the patch: "The patch is the result of two phases: code analysis and design of the patch. The code analysis, or reverse engineering, reveals the relevant code block, which overrides Skype's limitation for Intel's dual-core CPUs. The patch design isolates the minimal set of instructions that need to be modified to cancel this limitation." Windows only so far."

Comments

Re:Emulation would have worked too?

[yuriismaster]

The drop from 64 bit to 32 bit is one thing, however, in this case, the Skype code specifically queried the hardware for the GenuineIntel. If I remember this correctly from another /. post (not mine)

The opcode used in Skype, when activated on the processor, sets 3 4-byte registers on the processor as an identifier. This is burned into the silicon, basically.

For Intel Chips, the registers become
Genu, ineI, ntel - Genuine Intel

For AMD:
Auth, enti, cAMD - Authentic AMD

Like I said, since it's burned into the chip, there's no real way of 'masking' those registers as something else. This crack skips the verification, basically telling Skype that 'any processor is cool to run 10way' as opposed 'only GeniuneIntel chips can run 10way'

Re:Optimization is where?

[LLuthor]

due to use of Intel-only prefetch instructions or whatever

The AMD instruction set is a strict superset of the Intel instruction set. There are no Intel-only instructions anymore. There are however many AMD-only instructions (3dnow, 3dnow+, etc.), so if the situation were reversed, there might have been a legitimate claim, but since the AMD CPUs were locked out, it is clearly a bribe^Wmarketing descision.

Need Open Standards

[fastdecade]

Just goes to show why we need open protocols and open code for the future of VOIP. It's too important to leave to a single company, which is why I prefer SIP and clients like Google Talk and Gizmo where possible.

Re:Need Open Standards

[beasstman]

In fact SIP has supported dial in/out for years -- you can get termination for SIP compliant phones from Vonage, using Free World Dialup, or from smaller termination only providers (similar to Skype Out/In) like EXGN -- there are literally hundreds of them. ALL the commercial gateways sold by Cisco and the other major players are SIP to PSTN (regular telephone system) gateway (or Cisco proprietary Call manager -- but not Skype). Even Skype themselves in the backend is almost certainly using SIP to get to the public phone network for their Skype In/Out system, since none of the major gateway companies build anything else, and Skype isn't building one off hardware, it simply wouldn't be economically practical.

There is also signifcant work to make SIP P2P to eliminate the central servers http://www.p2psip.org/ from SIP going on right now. As an aside, Skype isn't really even that P2P -- it uses central auth servers, so it is more of a hybrid system -- ala Napster -- in reality.

And with a SIP phone you can use *any* of those SIP providers. With Skype, you have one choice.

Skype is very good at making things work out of the box, hence the popularity, but there really isn't much (if anything) it can do that SIP can't. It isn't even that the P2P mattered. Skype's success is a matter of a very nice UI and user experience. They gained market on ease of use and marketing -- not bad things mind you -- not better technology. Kudos to Skype for making it easy for users to use VoIP, which was (and still is) notoriously hard to use with other providers. But the technology is different to allow Skype to lock up users, not to make things better from a technical standpoint.

Re:"Arbitrary", but they already admitted it

[djtack]

In the first article on this deal that slashdot linked, Intel admitted the limit was arbitrary, and the result of a marketing deal:

But there are no specific instructions in Intel's current Pentium D or Core Duo chips that enhance the performance of VoIP applications, an Intel representative said. Skype is using an operation called "Get CPU ID" to identify the type of processor running on the PC. The Skype software has been preset to only accept Intel's chips as having the performance necessary to host conference calls of more than five people, the representative said.

Re:Interoperability?

[LocalH]

As far as I know, that was actually hashed out in Sega v. Accolade, where Sega was trying to prevent unlicensed cartridges by requiring software to contain the trademark "SEGA" and to write it at a specific hardware register (the infamous TMSS or "trademark security system"). The court found that it was legal for Accolade to include the TMSS for the purposes of making their own code work on the system, as the TMSS was initally intended to help fight counterfeiters (by counterfeiting such a cartridge, it would display the "SEGA" mark that shows up before all games on a Genesis 2 or 3).

For more indepth information, read Sega v. Accolade.