Home > Easy Open Air Cipher

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.

Any message that needs to be shorter or longer will be in the form of a 3 digit alpha/numeric preset code that for the message.

PRESETS: (P0x is given in clear)

P01 = Coordinates as follow in UTM - “YOD break HIN”
P02 = At way point - “Bravo”, etc. P03 = Moving to way point - “Charlie”, etc.
P04 = Aborting patrol route, returning to base
P06 = etc, etc, etc

EXAMPLE:

If you are interested and have read over how the system works (see (https://goto.pachanka.org/crypto/dryad-pad for full details) below is a quick example of it’s use to decode the following transmission giving 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?

Hint: you will need to convert UTM to Long/Lat for google maps.
Once converted just past in the search box… xx.xxxx,-xxx.xxxx

Or use.. https://www.geoplaner.com .
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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.