Joe -- how many bits are dedicated to the verify message?
I have considerable experience in crypto methods (used to teach graduate crypto 
class) and just need to know the limitations to perhaps find a suitable 
solution and maybe think outside the box here.  What we need is what I call 
"tactical" encryption.  Has to be good enough for long enough to prevent simple 
cracking.
Mike W9MDB



 

    On Wednesday, July 24, 2024 at 03:15:17 PM CDT, Joe Taylor via wsjt-devel 
<wsjt-devel@lists.sourceforge.net> wrote:  
 
 Understandably, a number of people have asked us about how SuperFox 
works.  I have explained that we are intentionally moving slowly and 
deliberately in our early tests, and we have not published source code 
or specifications in part because many details may still change.

The basic SuperFox scheme has been proven to work well.  It delivers the 
promised weak-signal gain of around 10 dB over multi-streaming FT8 with 
5 streams.  The present scheme will certainly be used for the Jarvis 
Island operations next month, but a variety of things could change after 
that.

Our goals for design of a SuperFox mode have included the following:

1. Constant envelope waveform, and hence up to 10 dB signal-strength
improvement over multi-streamed FT8.

2. Anti-piracy feature: a way to establish legitimacy of signal origin.

3. A way to prevent (or make much more difficult) misuse or our 
technology by derivative or modified programs, for example enabling 
robotic strings of QSOs.

4. Better use of available bandwidth: Fox should use (say) at least half 
of a ~3 kHz slice.

5. Better immunity to QRM, including deliberate QRM.

6. Operational aids for the Fox operator, including longer free text 
messages.

As you can see, technical details have been important in our planning 
but sociological, moral, and even legal issues are involved as well. 
Objective 2 in the above list involves cyber security matters, an area 
in which we have little expertise. Our weak-signal performance 
requirements demand small message payloads, and these are incompatible 
with (for example) most public/private key schemes.

For nearly all of its 24 year history the WSJT project has been entirely 
open source.  Ideally we'd like to keep it that way.  But objective 3 in 
the list is especially difficult (and likely impossible) to achieve in a 
fully open source project.

We appreciate all the help we have received in testing an early SuperFox 
scheme.  We hope many will work a new one when N5J operates as SuperFox 
from Jarvis Island.  We'll continue working toward a maxmially effective 
SuperFox design in the presence of many challenges, including possible 
software licensing issues, and we welcome all constructive input from 
other interested hams.  As always, our efforts are intended to benefit 
the wonderful hobby we share.

    -- 73, Joe, K1JT


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