So much has been written by greater minds than mine about secure communication in a crisis. There are many publicly available resources and information on SurvivalBlog and elsewhere.
Shifting letters in a message a certain number of characters is nothing new (Caesar Cipher, used in the last century B.C.). Using the SAME count to shift letters is a guaranteed way to have your encryption broken. Using different numbers to shift each letter in a message (a One Time Pad) – when your recipient has the same list of numbers to decrypt the message – is theoretically unbreakable, if you do it right.
This approach will only work if you have a list for the sender and a list for the recipient that is truly random. You can copy blocks of random numbers from several websites on the Internet [probably risky], or you can pretty quickly make your own table of random numbers with 10-sided numerical dice. Like this:
https://www.amazon.com/Chessex-CHX25408-Dice-Opaque-Black-White/dp/B077YC6JY1
This spreadsheet below (SFGshift) has been built to shift letters in a message. You type in the letters of your message, one letter per cell vertically, then you type in the numbers from your block of random numbers vertically. And the spreadsheet outputs letters that have been shifted the correct amount. Write down the encrypted letters and send that, either by email, or texting, or reading it letter by letter over the radio, or any one of several other methods.
When you’re done, you can select those two columns (message and numbers) and delete them, or just don’t save your changes when you close the spreadsheet, so the spreadsheet is clear for your next message. You can do the letter shifting by hand, of course, it’s just maybe a little faster to get your computer’s help (I wouldn’t do so on a computer connected to the Internet…). Or you can use a wheel like this:
https://www.giftofcuriosity.com/secret-codes-for-kids/
The spreadsheet here:
…can shift letters any number of characters, but for simplicity’s sake, I recommend simply using SINGLE digits from your block of random numbers.
You must enter the letters of your message in all capital letters!
Here is an example of how the spreadsheet encrypts and decrypts:
You can re-program the spreadsheet if you like. I’ve “locked” it using the code “12345” (which I’ve written right on the spreadsheet at F1 so everyone can get in and see how the spreadsheet works, if you want). If you’re an Excel guru, then feel free to experiment!
The longer you use the spreadsheet the faster you’ll get. Having two people encrypting or decrypting the message is even faster. You can encrypt longer messages by entering as much as will fit on the spreadsheet, recording the result, then clearing the spreadsheet and entering the next part of your message. This spreadsheet will only do 210 letters at a time and let that be an encouragement to keep your messages short!
This system will work. It will be more likely to fail through human error than a failure of the spreadsheet. (Hey, if you find errors, fix it and send the correction back to SurvivalBlog.com! I am a long way from perfect.)
To be extra secure you can break your completed, encrypted message into five-letter groups – word length is a clue to what the underlying word IS.
Keep your messages short. Only use encryption for your most important messages. Use code words and Brevity Codes to add a layer of complexity to your message. Here’s an example: BREVITY
The beauty of this Matrix (again, not my ingenuity) is that the top matrix can be reset with just two words that fit in the spaces provided. Believe it or not, you can find lists of words that are specific lengths – pages of 8-letter words, pages of 10-letter words, etc. (https://www.bestwordlist.com/4letterwords.htm) When you want to re-set the letter combinations, all you have to do is work the next two Key Words into an open message according to a pre-arranged method with the group or team on the receiving end.
The “Item Codes” section lets you assign words to each of those key items and concepts. Such as equating “rifle” with “stick” (you write it in), or “Danger area” with something like “quicksand.” Use your imagination. “I need 3 more sticks” would be your request for more rifles…
This printable Brevity Matrix gives you a way to send encrypted numbers as well. “I set” tells the recipient which row of letters you’re going to use. “I send” tells which letter in that row corresponds with the number you’re trying to transmit. Write your randomly-chosen words in the appropriate cells. A list of 9-letter words would be helpful! Or come up with your own system.
By mixing and matching encoding methods you’re making it harder for an unauthorized person to crack your codes. Of course, you can use these brevity codes in the open, you don’t have to encrypt them with random letter shifts. The beauty of Brevity Codes is they can be used rapidly and don’t require meticulous decryption!
I’d recommend changing your Brevity Matrix at least once a week. For really serious situations where you have a lot of away-from-camp activity you might want to change it daily…
The fact is, most of your messages will be pretty routine, not “top secret” stuff. Their value to an opponent will rapidly disappear after you’ve acted on a message or its utility has expired.
So now you’ve got two different methods – a true, unbreakable letter-shifting code and a Brevity Code worksheet that you can use together or by itself.
Be brief. Be clear. Keep it simple! Keep the circle of people with access to your blocks of random numbers small.
Work out a way to verify the identity of the person sending a message. This is especially important when you have more than one person or team on the radio. One strategy for an opponent is to pretend to be an authorized sender and transmit false information. This would be more of a danger for a team using just the Brevity Matrix because your teams in the field will be carrying that Matrix and it could be captured or copied. (“Man in the middle attack.”)
Be smart about how you transmit your messages. Radio is convenient but everyone can hear it (unless you’re both using low power and a Yagi antenna…). A courier is more secure, but possibly puts your courier at risk.
You could even play with internal word order randomization. Something like this:
Aoccdrnig to a rscheearch at Cmabirgde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
Or, you could substitute numbers for certain letters. (Note the SFGshift spreadsheet only encrypts/decrypts words, not numbers. You can still SHIFT numbers, you just don’t need the spreadsheet to help you!) Here’s an example from the internet:
7H15 M3554G3
53RV35 7O PR0V3
H0W 0UR M1ND5 C4N
D0 4M4Z1NG 7H1NG5!
1MPR3551V3 7H1NG5!
1N 7H3 B3G1NN1NG
17 WA5 H4RD BU7
N0W, 0N 7H15 LIN3
Y0UR M1ND 1S
R34D1NG 17
4U70M471C4LLY
W17H 0U7 3V3N
7H1NK1NG 4B0U7 17,
B3 PROUD! 0NLY
C3R741N P30PL3 C4N
R3AD 7H15.
PL3453 F0RW4RD 1F
U C4N R34D 7H15.
Train your radio operators with the information found at this link below, beginning with “Microphone Technique” and following. Good stuff here:
https://stringfixer.com/tr/Radiotelephony_procedure
There’s no end to clever ideas for communicating, but hopefully this will get you started and make your communications much more secure when they need to be! It looks to me like things are definitely about to get much more dangerous for all of us. And yes, it may well be the End Times, but our glorious King is coming, so take heart!
Trust God. Be prepared. We can do both. – ShepherdFarmerGeek