Easy Open Air Cipher

K7JLJ.com
01.12.19

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.

Because it's broken into (5) character sets it is easy to decode for 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 message that needs to be shorter or longer will be a 3 digit preset code that equals a pre-set message or checkpoint.

EXAMPLE:

If you are interested and have read over how the system works at (https://goto.pachanka.org/crypto/dryad-pad) for full details, but below is a quick how to.

Decode the following transmission to find the UTM of my local fishing hole.

MESSAGE

ME: "Base, this is Kilo One,  I authenticate Echo -  Romeo".

  1. Go to Column with "E" in it. Col_1
  2. Scan down that column until you see the first "R". Row_F
  3. Look directly to the right of that "R" and confirm with the letter your find. L
  4. Now Row_F is used to look up each letter and match a number in the column.

BASE: "Kilo One, I authenticate Lima".

We now know we have the same pad on both ends of the signal.

ME: "Base, message as follows... QXBLA   ENWQD".  (sounded out in Int. Phonetics)

BASE: "Kilo One, confirming... QXBLA   ENWQD".  (sounded out in Int. Phonetics)

[open image in another tab to read]

Can you find my location based off the DRYAD above?

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UTM Zone = 10T4 77129 and Easting = 48 03172
If you enter this as [Zone Northing Easting] with a space between each
[10T 77129 4803172] in Google Earth, it will take you directly to the spot, then you can lookup in google maps.

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. 

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