It is in the time of peace we establish norms for commuication within our groups. Encryption coding is nothing new and dates back hundreds of years. The simple riding into an enemy camp with white flag was a code of sorts. A subtle rubbing of the forhead may be a code. "Red Dog, this is Poutine, what's your DQ? The use of aboriginal language was another.
Even in peace time encryptioning is a good idea within your family. There are still enemies out there, and a lot of civil servants locking up people at our expense. Instead of playing monopoly, establishing a code would be hours of fun for everyone as we set up opposing forces, one to decipher and the other to make one up(Beta testing). First would be to establish a standard template. As faults reveal themselves, more complexity would be incorprated. At some time perhaps, the very young and/or weak individuals could be left out and things would get serious while a permanent template becomes adopted. This is the time that bare essentials are committed to memory and the bare essentials become the seed. It's best not to commit too much to memory. Neat ditty's and captions could be easily remembered as a key to the procedure to deciphering. They become the bow tie on the finger.
In my computer programming for my office. I was tasked with coming up with an encryption algorithim specifically for my department. I did some studies and settled on seven algorithims or templates for final selection. Not liking the idea that templates are in print for everyone to use, I created a hybrid. To this day my collegues in the department tell me the source code is still original and in use. The computer itself took the place of the "enigma machine", so the actual movement of parameters to their positions would need to be done by hand and pencil.
Into The Wrong Hands
In establishing the meat of a code, one needs to incorporate 'wrong hands' logic. This would occur when someone has been captured, or where under coersion, risk of divulging the code is a reality. Even transfering of individuals would trigger a code change within the group. Whatever the group deems should be done. With this in mind, perhaps the use of times of day would be a good strategy. This is when the encryption monitor(the one delegated) establishes a different template for half days or at time intervals of being sent. In the code itself is encoded the time of day/month/week/time sent(Not the top left hand corner where the date time is read and means nothing). "A sunny day today, Mom, but the snow clouds came over Old Man's Peak later". The rest of the letter is read according to a template that a list provides for that time(clouds=before noon)/day(snow=Wednesday), ie: template FY34.
Dealing with Human Censors
This depends on the degree of chaos. In times where the infrastructure has fallen and everyone is in a high degree of panic, group coded communication would be overlooked unless from a radio frequency reserved for the military and that would occupy much of their time, and that would be encoded anyway. If a letter should fall into a censor's hands for close scrutiny, it should be logical,in context and consistent in progression and mood, ie" greeting,elation, longing and finally hopeful with perhaps a "Say Hello to Mom" in closing that conveys longing to go home and whatnot.
A transmitted communication should have a hidden message, but also deliberate misinformation. The receiver should be aware of the ruse otherwise he'll ^&*% his pants.
. 'Poutine, those 10 cases of 7.62 came through, see you at XX56YT5". "See you" may mean "return from". Even a deliberate throw-off closing warning, "10-4 Poutine, Jeez.....keep it down man.". Remember never to convey a communication thought, but it should always be processed. Never establish patterns. if one is discovered build in a throw off. The method a reception should be taken should be coded as well. A "are you there?" could mean everything I say from now can be taken literally. A received "Yup!" = I will do so also, "Sure" = no, I will code.
It will take practice to get in that frame of mind. A reference notebook is risky, but if allowed in the group.
Over the public radio the French used a phrase to mean an action to be done in it's entirety by the resistance, or to send a message as to the results of a mission, or to initiate one. Usually the message was repeated twice or 3 times. "Le montagne et couvre avec la neige blanc"(my apologies to the French,... especially Mom
) I find this method too simplistic onit's own, but may find place in a hybrid. A code should not be recognized immediately as a code. There is probably a book out the describing the whole French code scheme. It would be interesting. Many of the resistance got captured on a regular basis. I'd hate to be the encrytion monitor in such conditions.
Template selection With Pen Subtlties
One could use the letter iteself to establish decipher templates. Every 3rd capital "T" could have a shorter right hand crossarm, or perhaps a date could have it, which could mean the resipient should use PY22 to decipher. A period with a slight tail viewed under a MF glass could indicate another.
Flip flopping can be used when the message doesn't need to make sense while it's transmitted or carried. If read, it is gibberish and is a mish-mash of letters. This type of coding is best done on a small, not even poweful computer or notepad. The template source code could be written in 20 lines of BASIC code. The program would read parameters of message code, password as a seed, and the type ie: decipher or cipher, and it would chunk out the message. These type of messages in code form would not make it past censors, but is probably the best for couriers when on a storage media like diskette or CD, as they are the safest as they would cause headaches and much time for the censor. They are great even now for hacker prevention. Even if a failed Yahoo or Gmail, the mail would be unreadable. Such programs are out there now, but remember others have it also.
If this code is received on a WalkieTalki, as tedious as that would be, it wouldn't be practical. You verbally state each letter/character in sequence, but it would take time of course and would be tedious doing a letter by letter swap by pencil. Best is, it would take ages for censors to figure it out. All characters are assigned an integer. So you would have 26 for the standard characters, and all the remaining special characters adding to 255 in all. It flip flops to a negative substitution table when a key character is hit. I'll leave food for thought here so you can figure it out and design your unique system.
In closing, there are many ways you can make up a code. Even key names or descriptions that are unique to your group can be used for the bases of your code. Uniqueness is a postive thing in code making. It's comforting to know that if there is a communication system allowed, you can fake it when faking is the only thing left to contact anyone. Even the morse code system can be turned upside down to make your own. Letter A may represent letter L etc. Perhaps a morse hybrid, with a code. Who knows.
Nice thing is we have the time to have fun making one while we wait.