Encrypt Phone Calls For Under $100

An anonymous reader wrote in to say "Seen on the IP list: a California company plans to offer a box that will securely encrypt your phone conversations, for less than $100 apiece. The company was founded by Cypherpunks who were upset about Clipper and wanted to create a good alternative. Looks like they're almost done. "

Comments

Re:Encrytion Not Secure

[Logi]

just let the task force break in to see how its set up

Not so. The article says they are using the Diffie-Hellman key-agreement algorithm, which means that there is no permanent key at all -- no private key to steal. Instead, the two units will negotiate a new key each time you make contact with someone, but makes no effort to ensure that you are talking to the right person. You are simply expected to know their voice or to recognize them in some other way.

They are using 2048-bit Diffie-Hellman which is about as secure as 2048-bit RSA. Diffie-Hellman is based on the discreete-logarithm problem and the best algorithms for solving that, given a large modulus, is pretty much the same algorithm that would be used to factor a large integer. The state of the art in factoring integers still below 512 bits, but is about to reach that mark. What is more, calculating one discreete-log will only give you the session key for a given session and no information about all the previous and subsecuent sessions, so it is even less appealing than trying to break RSA of the same size.

What the attacker can do is to launch a man-in-the-middle attack, so your box will talk to the TLA-agency's box in a secure manner, that box will be sitting next to another box talking to the person you really wanted to talk to. Then they just cross-wire the audio signal and tape everything. This, however, is a much more difficult attack to launch. You need more support from the phone-company and more hardware to pull it off.

It is also possible that the article is oversimplifying slightly and that there is some sort of identification going on in the hardware, but that would be much more difficult to use and people would frequently mess it up. The real problem in cryptography is key management. The rest is easy.