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Have you ever needed to send letter's and messages that are on strict a need to know basis, But your not quite sure how secure they are? Well today I'll be showing you a series of codes and ciphers that will be sure to keep out even the sneakiest of eye's, Some of them are simple and others are more difficult to crack! But what ever one you choose, You're secrets are no longer on constant alert, So let's begin!

Step 1: The Caesar Shift Cipher

This one is a simple alphabet cipher, But it's tricky to break without the right key, Each letter is moved along by a number let's say 5 for right now, So A would become F, J becomes O, Z becomes E and so on. The number is the key to the cipher here, So you could agree on a number before hand and then send messages afterward, Then only the people with that number can read the messages.

So for example "Meet me at the park" would become "RJJY RJ FY YMJ UFWP" with the number 5 as the key.

For the first cipher it works well, but the problem is that there are only 25 possible combinations (26 would take you back to the letter you started with). As a result, if there was someone who really wanted to break the code they could simply pold there way thruogh all 25 combinations. Admittedly, they would have to know in the first place that it is the Caesar shift cipher, So this only get's a difficulty of 1 star, It's over 2,000 year's old, after all.

Step 2: Number Code

This one is simple A = 1, B = 2, C = 3, etc., etc., all the way to Z = 26. Messages can be written using those numbers. This cipher is too simple to use on it's own, however, if you combined it with the Caesar code, It can become quite tricky, using it on it's own
"Meet me at the park" is " 13 5 5 20--- 13 5--- 1 20--- 20 8 5--- 16 1 18 11" Which looks difficult but isn't. Add a Caesar cipher of 5 and it becomes " 18 10 10 25--- 18 10--- 6 25--- 25 13 10--- 21 6 23 16" which should overheat the brain, If it's used in a full length letter. Once again, agree on a number beforehand. (used with the Caesar combination it get's a difficulty of 2 stars.)

Step 3: Pigpen Cipher

This one is a personal favorite of mine. Pigpen cipher is a code using symbols from a cipher key (picture above).
You write it out just as if you were writing a normal letter you still use spaces, commas, periods, etc. But instead of using letter's you use the symbols. I can't write out an example but the second picture on this page show's how it works. It isn't hard to figure it out if you have the key, Although, It is a rare kind of cipher, So the average person wouldn't know what it is, And it's hard to look it up when all someone has is a letter with symbols, so it's a difficulty of 2 stars for this one.

Step 4: Alphabet Ciphers

There are a number of these out there. Most of them depend on the way the alphabet is written out (Agreed beforehand between the group).

                     A   B  C  D  E   F G  H   I   J  K  L  M
                     N  O  P  Q  R  S  T  U  V  W  X  Y  Z
 
With this sequence, "How are you?" Would become "UBJ NER LBH?" All you do is swap the letter's around, Here is another example:

                    A   B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
                    Z  Y  X   W  V  U  T  S  R  Q  P O  N  M  L  K  J  I  H  G  F  E  D  C  B  A

In this one, "How are you?" would become, "SLD ZIV BLF?" It's worth remembering that even simple ciphers are not obvious at first glance. Basic alphabet ciphers may be enough to protect a diary or personal notes and they benefit of being easy to use and remember. Since there are a number of ways to do this cipher it's get 3 stars for difficulty.

Step 5: Code Stick

This is another favorite of mine.The most famous of the alphabet variations is a code stick---It was most famously used by the Romans.
Begin with a long strip of paper, Then wind it around a stick. It is important that the sender and the receiver both have the same kind of stick, two parts from an old broom handle would work great! I just used a pencil to show an example, normally a pencil is not a good option due to the fact that anyone can grab one. in the picture above the word "Instructables" is written down the length of the pencil, with a couple of letter's per turn of the strip. (you can hold it in place with a piece of tape so it's easier to write) once you unwind the strip of paper fill in the blank area's with random letter's, So in the end the strip of paper just looks like gibberish, but once it's wound around the stick again the message will be clear. It's a cipher that requires a bit of forethought, but can be quite satisfying.
For a matter of life and death, however, you may need the next method.

Step 6: Codeword Alphabet Substitution

You may have noticed a pattern developing here. To make a decent cipher, it's a good idea to agree on the key beforehand. It could be a number, a date, the title of a book, a word or even type of stick. It's the sort of added complexity that can make a encryption quite fiendish.
So let's get back to one of the earlier examples:

                    A   B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
                    Z  Y  X   W  V  U  T  S  R  Q  P  O  N  M  L  K  J  I  H  G  F  E  D  C  B  A

Now let's take this code and make it more complex by adding to it, If you added the word "island to it could become:

                    A   B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
                    I    S  L  A   N  D  Z  Y  X W V  U  T  R  Q  P  O  M  K  J   H G  F   E  C  B 

(This code depends on what row you take it from.) All were doing here is adding the word and taking out the letter's that spell it, Now "How are you" Switching out from the top row would becomes "YQF IMN CQH" Switching out from the bottom it becomes "UOJ DNX HQL" A whole new thing! Since this cipher can really be anything you want it gets a difficulty of 4 stars!

Step 7: Cipher Wheel

Now, last and not least, The cipher wheel!(A.K.A Cipher disk)This one takes a little more preparation but can be more secure than the others. You can make it from scratch or use this printable template I found online :
http://www.mountainvistasoft.com/chaocipher/BuildCipherDisk/Cipher-Disk-Template.pdf
NOTE : The third wheel in the template is used for another version of the cipher wheel.

( Read on even if you use the template). If you choose to to make if from scratch here are the directions to make one :

What you need :
Paper(preferably card stock)
A compass
Pencil
butterfly stud

Start by using a pair of compasses, trace and cut four circles out of the paper, 2 large---5 inches, and 2 small---4 inches
is a good size to use. Now a circle = 360 degrees, and there are 26 letter's in the alphabet so the spacing should be approximately 14 degrees. Mark off the segments as accurately as you can for both circles. When they are ready write the normal alphabet around the outside of the larger circles in the usual way --- A-Z. For the inner circles mark the letter's in random order, it doesn't matter how the letter's go, as long as it matches the the other code wheel. Finally place the smaller circle on top of the larger one and secure with a butterfly stud(It should spin freely). Your finished!

Now you're probably wondering, "how do I use it" well on the note write 2 key letter's like A-F (it can be different ever time to make it harder to crack). then line up the wheels with the key letters and write out the note using the random letter wheel(and use the A-Z one as reference). You should end up with a cipher wheel encrypter that can only be read by people with the other wheel! Since this one is only possible to crack with the wheel, It gets 5 stars for difficulty!
the problem with cyphers is that, even if you are using random symbols to represent letters, someone can hack at it using things like most common letters, common letter combinations, and two/three letter words to crack the code. some of this can be mitigated with intentional misspelling, slang, and pre-agreed code words. but some friends and i once created a whole new written language. this language was pronounced just like english but had three times as many characters. basically, english has 40 phonemes (the individual sounds we make in speech). so we made a "letter" for each phoneme. for example only one charater is used to make the CH sound, different characters for a long O and a short O, etc. we then added charcters for common prefixes and suffixes and even syntax words like 'the' and 'or' and 'and'. eventually we messed with the very structure of english by deciding that 'YOU' is the second person version of 'I' and 'HE' is the third person masculine of 'I'. eventually, using prefixes, suffixes, and modifiers, we had words for which there is no single word in english. surprisingly, this came out to a very intuitive code that we didn't even need a key for after a week or two of passing notes. we could just read it, but it would be very difficult for even a professional cryptologist to decode.
Nice to see the younger Futhark is still alive and well :)

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