Today I was looking again at an easy way to hide in plain site information I would want to send over VHF/UHF but do not want anyone to know.
I had previously looked at One Time Pads but gave up on them because of the difficulty of teaching someone how to use them. Without practice it’s just not intuitive so I’ve abandoned the idea more than once.
A close cousin is the DRYAD Pad. (https://goto.pachanka.org/crypto/dryad-pad)
The link above will allow you to generate your pads offline so it could be used off grid to make more, but I’ve pre-made (31) sets of them with unique ID’s for each day of the month.
One set is full letter size and in the comms binder at home, the other shrunk down on Rite-In-Rain paper for in the field.
This simple cipher pad is easy to learn and does what I need easily, which is primarily to send UTM Coordinates to update my base on my location and send short simple pre-set numeric message codes.
Broken into (5) character sets makes it easy to decode for the other users with the corresponding DRYAD since UTM is five / five for Long / Lat making my current location easy to find on a corresponding 1:24000 map I had printed from mytopo.com.
Anything shorter or longer will be a 3 digit preset code.
If you are interested and have read over how the system works at (https://goto.pachanka.org/crypto/dryad-pad) and want to take the challenge, try locating a local fishing spot based off this radio transmission…
ME > “Base, this is Kilo One, I authenticate Echo – Romeo“.
BASE > “Kilo One, I authenticate Bravo“.
Me > “Base, message as follows… YXJVI EDCYM“. (sounded out in Int. Phonetics)
BASE > “Kilo One, confirming YXJVI EDCYM“. (sounded out in Int. Phonetics)
Can you find my location based off the DRYAD above?
Hover over the xxxxx to see the decoded numbers and check your work.
Or click on this Google Earth.kmz file.
Works for me, hope it helps someone else.
PS> Even though this is a simple method, you still NEED TO PRACTICE it. When the wife and I go on a walk, we pick a spot and get the UTM, then I have her decode it and mark it on the map at home. Just like starting a fire in the rain, it takes DOING IT to be sure you can do it!