UPDATE (18 December 2014): I no longer recommend using Skype.

Skype is a free program that allows you to have secure voice conversations through your computer. It uses strong encryption and the sound quality is quite good. Encrypted text chat and file transfers are also an option. The interface is similar to that of AOL Messenger in that it allows you to create a list of contacts who are on-line. See:

http://www.skype.com

My Skype user ID is GeorgeMaschke.

Could you explain further the reason(s) for your belief that Skype Technologies can decrypt calls made using Skype? Is there some informed basis for your belief?

Since the discovery of any "backdoor" in Skype's implementation of 256-bit AES would be disastrous to Skype Technologies' goodwill (and ultimately its bottom line), it is hard to understand what would motivate the company to include such.

Note also that Skype communications are end-to-end encrypted by the users' computers, not by Skype Technologies'. The encrypted data packets that make up the communications are transmitted across a peer-to-peer network comprising hundreds of thousands of other Skype users. My understanding is that not all packets between any two parties necessarily travel the same route. And to the best of my knowledge, Skype Technologies has no capability of assembling the packets of any communication to which it is not a party.

Strong encryption does not depend on the alogrithm used being secret. If it were true that simply having the source code to encryption software necessarily enables one to decrypt any data encrypted with it, then why has no one cracked PGP, the source code for which has been public for more than a decade now?

The specifications for the Advanced Encryption Standard (AES), also known as Rijndael, is also public. Of course, it is possible that Skype's implementation of AES has some weakness that could be exploited by a would-be eavesdropper. But your suggestion that simply having Skype's source code would enable one to decrypt a Skype call is clearly not necessarily true.

The fact that music downloaders using peer-to-peer networks have been tracked down similarly does not entail that Skype conversations can be decrypted by third parties. In peer-to-peer (P2P) file sharing arrangements, users need to post to the P2P network a list of the files that they are making available for download. It is presumably this information that allows law enforcement to pursue those who unlawfully make copyrighted material available. For this purpose, I do not believe that it is necessary for law enforcement to assemble all the packets of a file transfer between third parties (something that would be necessary to intercept a complete Skype communication).

note: im just weary of anyone advertising free secure internet phone calls, despite the medium it encased in..and although you are not "advertising it" you advocate it,  and how would i really know that you don't have the capability to do what i mentioned?

yes the first thing i said was uninformed speculation, i don't know a thing about that company, nor do i claim to.  i can not provide proof that this can be done other than the common computer knowledge that anything done by a computer can be undone by a computer..anything..if there is a side that is meant to decrypt this, than there is someone other than the person meant to receive it who can find out what you are saying as well...i don't claim to do it...and i don't care to try...the only experience i have with this area is writing programs that encrypt/decrypt information...and i have a limited understanding of how packets are transferred and composed within different protocols....in all reality im this free internet phone is probably safe, but im always the skeptic, and what reason would you have to defend them so quickly and adamently anyway?

in theory there would be a way in which you could decrypt this as fast as the target, whether it takes additional installation of software on the target's computer or not...which was physically placed there..coupled with the software or magically positioned...etc.  it would take you a billion years to decrypt it if you were using the nazi's enigma machine and trying to stumble on the key.  the key would be stealing the key, or having access to the key maker....haha ok ok, this is starting to sound like something familiar

compscigeek wrote on Nov 2^nd, 2004 at 8:40am:


compscigeek,

While this may sound reasonable, it is really quite hard. So much so that even the simple problem of finding any two 17 byte sequences that produce identical 16 byte MD5 digests has never been solved and it can be easily shown there are zillions of them.

AES and >1500 bit RSA for key exchange is believed to be far harder than this.

Any program may have a backdoor or, even more likely, bugs and that is where the risks are. To learn more about cryptography, a free book on the web "Handbook of Applied Cryptography" will provide you plenty of info and references.

You say you have written programs encrypting/decrypting packets. Was this a school or work project? What algorithms did you use?

-Marty

According to www.skype.com they have "served" over 2 billion minutes of conversation.

If you believe the info at the bottom of this page:
http://www.skype.com/help/faq/#1billion
Quote:


Then I think the liklihood of "Big Brother" listening in is pretty low.  Think about it.  2 billion mintes of encrypted voice calls, all routed throuh multiple points on the Internet.  No magic vacuum machine computer can suck down all that data then decrypt it, then convert it, despite what Hollywood and Tom Clancy make you think.

I doubt "Big Brother" cares to listen in to your calls in the first place.  But I wouldn't have any reservations about using Skype.  It is no more dangerous than any other program you didn't personally write.

Believing that Big Brother has these capabilities is the same belief system that makes the polygraph successful.  Big Brother's use of the polygraph is the system that keeps smart engineers that can actually build good surveillance systems in private industry making programs like Skype instead of on the government payroll protecting us from bad guys.