ee5391aa@hydra.unm.edu (Duke McMullan n5gax) (10/19/89)
In article <OTTO.89Oct17163149@tukki.jyu.fi> otto@tukki.jyu.fi (Otto J. Makela) writes: >Preventation: does anyone know of cheap but reasonably reliable scramblers ? Ahhh -- I won't insist that those are mutually exclusive, but.... Cheap and easy to defeat -- sure. There was one in last year's Electronic Ex- perimenters' Handbook (Popular Electronics). It's a simple double-balanced modulator used to invert your voice signal. It's cheap. It's easy to build. It's easy to defeat. Expensive and hard to defeat -- sure, again. There are several manufacturers in the business. A really good one digitizes the voice and performs an en- cryption/decryption in the digital domain. Very, very hard to defeat. Very, very hard to afford without corporate or government funding. Expensive and easy to defeat -- probably. I've heard (that's rumor mill level, so I don't take it too seriously) that some outfits make dippy double-balanced modulators and sell 'em to the marks for kilobucks, then run like hell. I don't know anything about it from personal experience, but still, there are a lot of goniffs in this sort of business. Cheap and hard to defeat -- I don't think it exists, but it could, and the technology is HERE TODAY! It actually wouldn't be hard to integrate the whole schmeer, including D/A, A/D, key management, (en/de)cryption, and an automatic slicer-dicer for carrots all on the same chip. The thing that would make it cheap is volume production, which probably won't happen, at least not soon. Various Government Agencies (read: Big Brother) don't want powerful crypto- graphic technology to get into the hands of T.C. Mits (and, really, I don't blame them) since it would make their job much, much more difficult. The technology is currently there for very secure voice "scrambling", but it is still a mucho bucks proposition. The VGAs can live with this; there just aren't very many of their ENEMIES who have the finances to play with this stuff on any significant scale. Those who do -- the drug "wholesalers", the Mafia and other organized crime, etc. -- are a minority who can be bugged in other ways. What most people don't realize (and I'm sure the VGAs do, but don't like to publicize it -- for obvious reasons) is that anyone with a computer has a very powerful cryptographic device at his disposal. It's not up to doing real-time voice encryption (you need customized & dedicated hardware for that), but if you don't mind communicating in blocks (write a letter, encrypt it, call up your friend, enmodem the message, etc.), it'll work just fine. Use reason- ably sophisticated algorithms, and none of the VGAs will be able to cryptanalyze your stuff effectively. They MAY crack it with other techniques, such as "practical cryptanalysis" -- stealing the key. Physical security is another problem altogether, one you can't ignore. But that, as the textbooks say, is beyond the scope of this discussion. I'm tired; good night. Hope it helps, d "In all levels of life, the sheep are only safe when the wolves are not hungry." -- F.J. Lovret Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu
ee5391aa@hydra.unm.edu (Duke McMullan n5gax) (10/19/89)
Re. that last, sorry if the approach to cryptography seemed simplistic.
Really, I _really_did_ think I was posting on sci.electronics.
It's even later than I thought.
G'night!
d
"In all levels of life, the sheep are only safe
when the wolves are not hungry." -- F.J. Lovret
Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edukadie@herodotus.cs.uiuc.edu (Carl M. Kadie) (10/19/89)
>In article <OTTO.89Oct17163149@tukki.jyu.fi> otto@tukki.jyu.fi (Otto J. Makela) >writes: >>Preventation: does anyone know of cheap but reasonably reliable scramblers ? In article <790@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes: ... >Cheap and hard to defeat -- I don't think it exists, but it could, and the >technology is HERE TODAY! It actually wouldn't be hard to integrate the whole >schmeer, including D/A, A/D, key management, (en/de)cryption, and an automatic >slicer-dicer for carrots all on the same chip. The thing that would make it >cheap is volume production, which probably won't happen, at least not soon. Everyone needs this technology. On National Public Radio last week there was a story about baby monitors. These are wireless devices that parents use to listen in on their baby's room. The devices work like a sensitive one-way walkie-talkie. The problem: Anyone with a radio scanner can hear just about every conversation in your house. There is a similar problem with cordless phone. Cellular phone can be heard on older scanners. Any solution that tries to outlaw such monitoring (although it is illegal to monitor cellular phone calls) is doomed to failure. [You just can't stop people from listening to radio signals that enter their house.] The technological solution to this technological problem is much better -- scramble the signals. There is precedence: HBO solved (most of) its problem with home satellite dish owners by scrambling. - Carl Kadie Carl Kadie University of Illinois at Urbana-Champaign ARPA: kadie@m.cs.uiuc.edu
henry@utzoo.uucp (Henry Spencer) (10/19/89)
In article <790@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes: >Expensive and easy to defeat -- probably... Most any non-digital scrambler, no matter how tricky, is probably going to fall under this heading. There is lots and *lots* of redundancy in the human voice, and it's very hard to hide it completely. In WW2, somebody at Bell Labs (I think it was) discovered that the then- current top-security scrambler system could be understood with the unaided ear after a bit of practice. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
agn@unh.cs.cmu.edu (Andreas Nowatzyk) (10/20/89)
>>Expensive and easy to defeat -- probably... > >Most any non-digital scrambler, no matter how tricky, is probably going to >fall under this heading. There is lots and *lots* of redundancy in the >human voice, and it's very hard to hide it completely. Not necessarily true: the (west) german police uses a system that digitizes speech, cuts the data in short blocks, permutes the order of these blocks according to a digitally computed key, converts it back to analog and sends it. A key tone is added to synchronize the receiver so that it can undue the process. The system is not easy to defeat and has the virtue of using no more bandwidth than the original signal. This point is important to be able to use it over existing gear (radios, phone lines, etc.). While a full digital system is possible in the same bandwidth, the complexity is much higher and more likely to break down under marginal signal conditions, interference, and routine day-to-day use. -- Andreas -- -- Andreas Nowatzyk (DC5ZV) Carnegie-Mellon University agn@unh.cs.cmu.edu Computer Science Department (412) 268-3617
hkhenson@cup.portal.com (H Keith Henson) (10/20/89)
ee5391aa@hydra.unm.edu (Duke McMullan n5gax) posted: "anyone with a computer has very powerful cryptographic device at his disposal. It's not up to doing real-time voice encryption (you need customized & dedicated hardware for that . . ." I wonder--at some point PC's will be up to realtime voice encription. Be an interesting software market when they do. Keith Henson
johnl@n3dmc.UU.NET (John Limpert) (10/20/89)
In article <1989Oct19.154929.19256@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <790@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes: >>Expensive and easy to defeat -- probably... > >Most any non-digital scrambler, no matter how tricky, is probably going to >fall under this heading. There is lots and *lots* of redundancy in the >human voice, and it's very hard to hide it completely. I read a book on HF radio frequency assignments that said the Department of Energy used a scrambler system for the trucks that transport nuclear materials. The system divided the audio spectrum into a number of frequency bands and shuffled them around before feeding the audio into the transmitter. The interesting part of the system was the use of some sort of key generator to change the mapping at a rapid rate. I don't know how difficult it would be to reconstruct the original signal by attempting to match up parts of successive samples. The nice thing about this system was that it worked with conventional radio equipment. -- John A. Limpert I'm the NRA! Internet: johnl@n3dmc.UU.NET UUCP: uunet!n3dmc!johnl
scott@perle.UUCP (Scott Allen) (10/20/89)
In article <790@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes: >In article <OTTO.89Oct17163149@tukki.jyu.fi> otto@tukki.jyu.fi (Otto J. Makela) >writes: >>Preventation: does anyone know of cheap but reasonably reliable scramblers ? [stuff deleted here] >Cheap and hard to defeat -- I don't think it exists, but it could, and the >technology is HERE TODAY! It actually wouldn't be hard to integrate the whole >schmeer, including D/A, A/D, key management, (en/de)cryption, and an automatic >slicer-dicer for carrots all on the same chip. The thing that would make it >cheap is volume production, which probably won't happen, at least not soon. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ I'm not too concerned about scrambling the signal on the lines. What does bother me is that when I use a cordless phone, anyone close by can listen in to the radio signal without tapping the line. Producing a cordless phone with encryption between the handset and the base may be a good incentive for volume production of such a chip. (A switch could be provided so that two of the same type of phones could also encrypt end to end.) -- ========= * Scott Allen * UUCP: P E R L E * Perle Systems Ltd. * ...!uunet!mnetor!perle!scott ========= * Scarborough, Ontario, Canada *
neal@lynx.uucp (Neal Woodall) (10/25/89)
In article <6596@pt.cs.cmu.edu> Andreas Nowatzyk writes: >>There is lots and *lots* of redundancy in the human voice, and it's very >>hard to hide it completely. >Not necessarily true: the (west) german police uses a system that digitizes >speech, cuts the data in short blocks, permutes the order of these blocks >according to a digitally computed key, converts it back to analog and sends >it. I have heard of systems like this, and I think that some government agencies (maybe the Secret Service) tried them for a while. The Secret Service now uses Motorola's DES system. Another system that is available on the open market here in the US is the so-called "split band rolling code" scrambler. It is a combination of digital and analog technologies, and offers reasonable voice security at a decent price. These systems are designed to be used on common commercial two-way FM radios. Basically, the system spilts the voice band into two pieces (upper and lower)....there are 32 possible split-points. When the voice band has been split, each piece of the band is inverted, then the two inverted pieces are recombined and transmitted over the radio channel. The neat trick is that the split point in the voice band is changed from 4 to 60 times per second, controlled by a "rolling code", which, from what I can gather, is a pseudo-random generator.....the seed that you choose determines the code sequence that splits the voice band. To maintain sync, the system transmits a sync-burst every second or so....this allows people to join a conversation in progress (if they have the key!). A very robust error correction system ensures that the sync burst gets through noise. Integrated circuit designed for the various functions needed are made by MX-COM in Winston-Salem, NC. If you are so inclined, I feel certain that some of the IC's available could be adapted to use in a phone scrambler. Neal
barr@caen.engin.umich.edu (William Barr) (10/26/89)
In article <1989Oct19.143522.7686@ux1.cso.uiuc.edu> kadie@herodotus.cs.uiuc.edu.UUCP (Carl M. Kadie) writes: >>In article <OTTO.89Oct17163149@tukki.jyu.fi> otto@tukki.jyu.fi (Otto J. Makela) >>writes: >>>Preventation: does anyone know of cheap but reasonably reliable scramblers ? > >In article <790@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes: > ... >>Cheap and hard to defeat -- I don't think it exists, but it could, and the >>technology is HERE TODAY! It actually wouldn't be hard to integrate the whole >>schmeer, including D/A, A/D, key management, (en/de)cryption, and an automatic >>slicer-dicer for carrots all on the same chip. The thing that would make it >>cheap is volume production, which probably won't happen, at least not soon. I've seen a device that fits over your phone advertised in this last summer's issues of High Times (what? You don't read HT?) . Basically you have one at each end and it fits over the handset. It has a keypad and allows some fairly large number of possible codes. The person on the other end must be using the same code. I'm pretty certain it was digital. I believe that each handset device was about $100. It seemed fairly reasonable.