General Category > Tactical Corner

Sending Encrypted Messages in Morse Code.

(1/6) > >>

In this article I will show you how to send an encrypted message that can not be broken. All you need is paper and pencil. With our privacy disappearing faster than the Mountain Gorilla, I thought that such knowledge might one day become more than a coffee shop conversation topic. I am referring to the One-Time-Pad described by Neal Stephenson in his novel, "Cryptonomicon." Highly recommended by the way. So, learn it and have fun with your kids. It's kind of like showing them how to start a fire without matches or lighter. It's fun, and who knows, they might have to use it some day.. By the way, this is one more reason to learn Morse code. You can't encrypt your voice, at least not without exotic hardware and software. After a natural or man-made disaster, our country could be a prime target for invasion. I know, extremely unlikely.. So thought many Europeans in 1939. Sending a coded message with a simple and small CW radio might one day be a life saver. DO NOT send encrypted messages over the airwaves, it is illegal! I have always been interested in encryption theory. Surprising, since I never liked puzzles or crosswords. Not to mention my poor math skills. For some reason I have always been driven to learn obscure, odd or outdated skills. Even though I am a programmer by trade, the level of complexity in encryption software is way over my head. I've had a PGP key for about fifteen years, but to my dismay, nobody ever sends encrypted messages but for the occasional server password; and that may have been two or three emails in ten years. Had I not insisted on it, I would have received none. You would think this feature would be built in every email program, but it isn't. You must add a plugin to your mail client, if one is even available. I know Evolution on Ubuntu has it built in, and Pegasus Mail on Windows has a plugin, my Mac does too. But computer encryption is not the subject today. Let's see how it is done. It is pretty easy: You need a way to produce random letters. These random letters will be the key used to code and decode the message. Do not rely on yourself or a computer to produce true randomness. Typing random keys on your keyboard doesn't work, it won't be truly random. Good for practice, but not for real messages. I would suggest putting letters from a Scrabble game in a bag and shake it vigorously. Pick one letter (without looking!), write it down. Put it back, repeat. Write down your pad in groups of five letters, like so: GEXOJ AXYEN LOWHD AWQJD UBRWJ You need as many letters as your intended message. Here is a one-time-pad generator, for practice (set group length and key length to 5). Encoding: Now, let's say your message is HELLO. Our first key group is GEXOJ. HELLO is the message.
GEXOJ is the key, called a one-time-pad because it can be used for only one message. We are going to count to the position of the letter H, but starting at zero, not one.
0 1 2 3 4 5 6 7........ Etc... Here is the whole alphabet to help you: ABCDEFGHI JKLMNOPQRSTUVWXYZ 012345678910111213141516171819202122232425 H=7.
Our first key letter is G, and G = 6.
Add the two: 7+6=13 = N.
We keep going: E=4 + E=4 = 8 which gives I.
L=11 + X=23 = 34 ! Ha, problem! The alphabet has only 26 letters.
No problem, when we hit 26, we go back to A. 27=B, 28=C, etc. So, 34=I.
L=11 + O=14 = 25 = Z.
O=14 + J=9 = 23 = X.
Here is another way to look at it: Position74111114 MessageHELLO Position6423149 KeyGEXOJ Position138342523 EncryptedNIIZX Our secret message is NIIZX. Now, let's decode it:
We do the same thing in reverse...
(If a number is negative then add 26 to make the number positive.) EncryptedNIIZX Position138342523 Minus (key)6423149 Equals74111114 MessageHELLO The encrypted message is as random as the key is. Therefore, as far as I know, there is no code breaking method available that could possibly crack it. Your message is of course only as safe as the key. If the key is truly random, has not been seen by anyone except you and the recipient and was used only once then destroyed, then your message is safe! Gil.

Cryptography is one of the most interesting subject in mathematics and logic.  When it comes to Amateur Radio, where you rightly point out that we cannot use cryptography or cyphers of any kind, I am reminded of one of my favorite TV series, In Plain Sight.  The "Where's Waldo" approach to Amateur Radio communications can be quite useful.  Tactical communications are some of the most difficult to "Waldo-ize" but a little thought and a cool delivery can pull it off.  You don't have to say, "There is a dead guy in a burned out car in front of the sewer plant!" on local repeater but you can direct the right person to that location with something like "You are needed at 2929 West Lake Ave, please expedite." 

When it comes to digital communication, Amateur Radio can Waldo-ize much more thoroughly.  This is my preferred list from least Waldo-ish to the most Waldo-ish.

1) VHF Packet (Not commonly intercepted, but easy to do so)
2) Sound card modes: PSK31, Olivia, Thor, MT63, etc.  (Easy to intercept, but what casual listener has the equipment?)
3) CW (Who'd bother with so much easier pickings on the local FM repeater?)
4) Pactor III  (Expensive and difficult to intercept.)
5) Winlink / Winmor (Very difficult to intercept-- especially peer-to-peer mode.)


Keith, K7KEV

I'll +1 K7KEV, and add D-star / All-star.  Especially D-star, because come on.  NOBODY has that gear.

Security through obscurity, eh??

Jonas Parker:
Formulab has a nice  little and free program for generating One-Time Code Pads... Great fun for the kids on a rainy day!  8)

K7KEV  I like "hidden in plain sight"  CW  :)

Nice well thought out post above.  73


[0] Message Index

[#] Next page

Go to full version