From: john@anasazi.com (John R. Moore)
Subject: Re: 800MHz Trunked Radio System Signals
Reply-To: john@anasazi.com
Organization: Anasazi, Inc.  Phoenix, Arizona USA
Date: Wed, 30 Dec 1992 15:57:13 GMT

Keywords: 

In article <1992Dec30.061944.7061@timesink.chi.il.us> mikebo@timesink.chi.il.us (Michael Borowiec) writes:
]In article <1992Dec29.180128.21441@anasazi.com> john@anasazi.com writes:
]>In article <92360.134725PJB113@psuvm.psu.edu> me <PJB113@psuvm.psu.edu> writes:
]>]As more and more services switch to trunked systems, I'm sure the scanner
]>]companies will eventually develop scanners with trunking capabillities. I
]>]strongly believe that the same thing is true with digital encryption. Too
]>]much money is involved in communications monitoring for it to go down
]>]the tubes just because of trunking and encryption. -PJB
]>
]>A couple of problems with this:
]
]>  (2) It is illegal to receive digitally encrypted signals. I don't know
]>      if it is illegal to build decryptors, but if it isn't, it would be
]>      quickly.
]
]I don't think you can outlaw a thing... only the illegal use of a thing.
]There are exceptions however, such as drugs and dangerous weapons. I don't
Sorry, but you can indeed outlaw a thing. The Electronic Communications
Privacy Act of 1986 specifically OUTLAWS receiving encrypted signals
unless you are the intended recipient. This is the same (ill conceived)
law that outlaws receiving cell phone calls but leaves it legal to
receive cordless phone calls. Go figure...

]think an electronics hobby kit would fall into this catagory. That's how
]companies get away with selling cable de-scramblers - in kit form.
Yes, but they COULD outlaw these kits. However, it is moot (see below)
]
]>  (3) The digital encryption schemes are quite strong. I doubt that you
]>      could afford a scanner that could decrypt them (without knowing the
]>      key beforehand). Such a scanner would probably cost at least
]>      $20,000,000 (in order to crack the DES code). Now, you are probably
]>      going to respond "yeah, but they cracked the Videocipher" to which
]>      I shall pre-emptively respond: "Yes, but that's different."
]
]I dunno about the $20M part. (-8  Now you can buy a 50MIPS machine
]under $5000. Within a year or two, you'll be able to buy a 100MIPS
]machine for the same $. The DES code is only RELATIVELY secure. Just
]read anything on the NSA if you doubt that. They eat DES encoded
]messages for lunch. The US Government wants to establish the DES as
]a standard so they can read your mail while still permitting you
]RELATIVE protection from your competitors. Note that vendors sell
]two different types of DVP equipment: one for businesses/consumers
]the other for government use.

Yes, DES is relatively secure. However, the most recent cryptography research
that I have read about claims that they believe DES is about as secure as is
possible with a 56 bit key. That means you need an exhaustive key search
(2^56 keys). At 100 Mips, you could figure maybe 100,000 tries per second?
That would yield 548 YEARS of decryption time. Now, it is ALLEGED that the
NSA eats DES messages for lunch, but I would point out that 20 million dollars
for a specialized computer is peanuts to the NSA. I doubt they eat them
for lunch with a few 100 MIPS computers!

By the way, it is even more secure with voice encryption, because once you
have it decoded, how can you tell that you have the right plaintext? More
processing required. Most text info, on the other hand, is easier (letter
frequency tests, parity bit tests, etc).

Now, it is true that they could screw up the job, and leave critical information
laying around (like the Videocipher-II did), or you MIGHT be able to find
a tiny trace of the audio laying on the carrier (from power supply feedback),
but I doubt it.


-- 
John Moore NJ7E, 7525 Clearwater Pkwy, Scottsdale, AZ 85253  (602-951-9326)
john@anasazi.com ncar!noao!asuvax!anasaz!john anasaz!john@asuvax.eas.asu.edu
 - - A conservative is a liberal who has been mugged by reality! - -
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