[Milsurplus] Cipher Challenge!

[Bob Camp]

Hi

Which is why I proposed something that allows you to practice, but it  
entirely self contained - just like data compression .....

Bob


On Nov 7, 2007, at 11:03 AM, mikea wrote:

> On Wed, Nov 07, 2007 at 10:15:53AM -0500, Ray Fantini wrote:
>> For well over twenty years the amateur satellite community has used  
>> a common algorithm to encrypt all 9.6 Kbps digital satellite  
>> traffic, the call letters of the originating station and of the  
>> satellite are transmitted in the clear but all other text is  
>> encrypted. not for any clandestine reason but to avoid having long  
>> strings of ones or zeros. the software and the encoding algorithm  
>> are all public knowledge and can be downloaded from many sites. I  
>> have done quite a bit of satellite operating and have never heard  
>> any complaints about using encryption. Everything that I  work with  
>> in digital television and radio has to be encrypted, not just to  
>> avoid long strings of similar states but also for forward error  
>> correction and I would speculate that anyone involved with modern  
>> digital communications beyond 1.2 Kbps is going to be using some  
>> form of encoding or what the outside observer would consider  
>> encrypted data. I have not worked with the DSTAR format yet but  
>> with its AMBE encoding scheme and Forward error correction is  
>> impossible to decode with out the proper software, so dose this  
>> mean ICOM is braking the law? And with  the ARRL promoting this  
>> format as the future of Ham radio are they law breakers too?
>> Ray Fantini KA3EKH
>
> No, neither the satcom folks nor the DSTAR users are breaking the law,
> because the algorithms have been provided to -- *and* accepted by --
> the FCC, and because DSTAR falls in with AMTOR, PACTOR, GTOR, Clover,
> and other accepted digital codes.
>
> Also, there's an explicit authorization in Part 97 for the satcom
> folks to encrypt the command packets that control things on their
> birds, so that only the authorized operators can control "their"
> satellites.
>
> It's the hams who decide they're going to encode or encipher their
> comms without providing
> o	algorithms and keys (for ciphers), or
> o	codebooks, superencipherment tables and keys (for codes)
> to Uncle Charlie,
> or who use other than the approved SS methods, that can wind up in a
> big heap'o'trouble.
>
> 97.113 is very explicit on that subject:
>
> :    ' 97.113 Prohibited transmissions.
> :      (a) No amateur station shall trans-
> :    mit:
> :
> :      (1) Communications specifically pro-
> :    hibited elsewhere in this part;
> :
> :    [snip]
> :
> :      (4)
> :    [snip]
> :    messages in codes or ciphers intended
> :    to obscure the meaning thereof, except
> :    as otherwise provided herein;
>
>
> So it would be A Bad Idea, for instance. if I and another ham were to
> decide to encode our communications using the WW II training codebook
> found at <http://mikea.ath.cx> to encrypt our communications, unless
> we get permission first -- which may or may not be forthcoming. The
> same holds true if we decide to use Hydrographic Office Pub. 80, two
> codebooks for use in merchant ship communications, even though that
> publication is intended and approved for certain non- amateur-radio
> communications, and is published by the U. S. government.
>
> It would be at least as bad an idea if someone else and I decided to
> use a different shift register tap pattern, size, etc., than those
> set out in 97.311 for DSSS, or a different FH scheme from that set out
> in the same place, because at that point reading our signals requires
> cryptanalysis, rather than running the signal through an RX set up to
> read signals compliant with 97.311.
>
> An idea that occurs repeatedly in Part 97 is that encoding is not to
> be used to obscure the meaning of a transmission, except for control
> of a space station.
>
> But you all know this already.
>
> -- 
> Mike Andrews, W5EGO
> mikea at mikea.ath.cx
> Tired old sysadmin
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