At 07:34 PM 1/24/96 -0600, Andrew Loewenstern wrote:
Don't high speed modems transmit and receive on the same frequencies, using echo cancelation to decode the receive signals? Does that make it impossible to eavesdrop on high-speed (i.e. V32bis) modems?
No, and a lot of crackers and phone phreaks found out the hard way. You can buy protocol analysers off-the-shelf that will give a dump of the entire communication by just passively listening in (or possibly playing back a recording).
Assuming it were possible, it would have to have a rather good quality, although DAT should be adequate, I should think.
I have seen units that could decode all of the popular Blue Book protocols for consumer equipment such as faxes and high-speed modems as well as ISDN, T1, DS3, ATM,
Hey! Justa sec! ISDN is basically digital (broadband), so (obviously) is T1, likewise DS3 and ATM. Except for ISDN, unidirectional signals (at least at one time...), I think. This is NOTHING compared to the difficulty of doing simultaneous bidirectional analysis in a 3 khz bandwidth of 28 kbps each way! Maybe you're far more familiar with what equipment is available for telephone analysis than I am, but I have serious doubts that the capacities you list above are even close to what the other guy asked about. etc... Most are programmable and some are full-blown
computers running stripped down versions of Unix and can also be controlled over the network from RealComputers. With multiple analysers and a little custom software you could easily perform MITM attacks. The hardest part is getting in the middle.
Modulation, comm-protocols, and compression techniques are not a replacement for honest to goodness crypto.
Agreed, but let's not underestimate the amount of effort involved. This is important, because of that "Digital Telephony" bill crapola they're trying to foist on us. Their argument will be, we presume, that "we've gotta be able to bug all these lines because of all the drug dealers talking on the phone. Well, unless the government is proposing installing the capability of bugging data the vast majority of data calls (including those that, hypothetically, use Clipper) then they're NOT going to get any traffic they claim to want to hear. We should ask, "How much will it cost to even UNDERSTAND a data phone call, let alone decrypt it, and if it's too high let's give up while we're behind."