Skip this step if you'll be using already existing ciphers, such as Caesar's cipher. When creating ciphers for stacked codes, don't worry about making them hard to decode. Even simple ciphers can go a long way when working with rules.
 For the purpose of this article, the example uses the sentence "Hello World". Start with Caesar's cipher."Hello World" would become Ifmmp xpsme if we switched it one to the right.
 It can be very frustrating to work hard on your message, only to find out that it's wrong. A simple typo or miscalculation can be disastrous. Ifmmp xpsme can easily become fmnp xpsme, which translates to elmo world. If you live in a town that has a theme park called "Hello World" and a children's playground called Elmo World, and your message is "Meet at...", the result would be a mess-up! Check, double check, and triple check if it's that important.
 For this example, use the substitution cipheron it. You can use any substitution you want, this example uses:


Applying this cipher, you will get: Wkhha qachv. The benefit of using stacked ciphers clearly shows up here. Anyone who tried to decode this would have a very hard time finding a pattern, with two ciphers applied.
 As stressed above, double checking is needed, especially when dealing with stacked ciphers.
 Three ciphers stacked will probably be enough. More than three will be too complicated for you, and especially your friend, to decode, even with the key laying beside you. While more than three is too many, less than three can be easy to decode. Don't use substitution code or Caesar's code more than once. Try another kind of code, such as a symbol code.


Use phone code now. Phone code relies on the keypad of a phone or cell phone to do its work. If you look at a phone, you'll notice that the letters in small print under the number start at 2. 2 = abc, 3 = def, 4 = ghi and so on. To write in phone code, jot down the number that corresponds to the correct letter, then add a dot either to the left, on top, or to the right of the number. For example, to write b, write a 2 with a dot on top. To write L, write a 5 with a dot to the right of it.
Go ahead and write the message, Wkhha qachv, in phone code. Note that some numbers have 4 letters under them; for these, carry on the same, but for the last letter on that number, put two dots to the right. Look at the seven in the following image, you'll see two dots for s.
Your phone code should look like this:
The stacked cipher can now be illustrated by the following image:

, The problem with all this so far is that a certain letter or number will still represent the same letter, even if you stack many ciphers on your message. But if you add rules, they'll allow for inconsistencies in your cipher, which makes it harder to decode. Rules are what throw off a "spy" or nosy person the most. With rules, you're not bound down by the normal ciphers that can easily be cracked; and you can't just "guess" what certain words are. An example rule would be: "Every other word, the Caesar's cipher is applied by two." This means that every other word, instead of A = B, it's A = C, B = D, and so on. If someone found out what wkhha means, they wouldn't be able to apply it to every wkhha in the code, because some would be different. The next steps explain how to make and apply rules.
 Come up with something creative. Think of grammar, and use rules such as "after each a, the next letter is one up in the alphabet." You could even go incrementally (each word goes up one in the alphabet.) So "Hello World" would be Ifmmp Yqtnf, instead of Ifmmp Xpsme. (The second word, "world", goes up two in the alphabet instead of one.) Although going up incrementally would be very hard in a code that is more than ten words long, it is useful in messages less than ten words long.
 Applying rules gets tricky, especially if you make them once you've finished writing the message in code. Once applied, though, a rule will stump any spy who tries to read your messages. Once you've applied your rule, double check your work.
 Write out a list of the rules you have, and give it to your friend. That way, you never have to send a message in the same code again. (At the top, you can just write Applied Rule 1, 5, and 7, then whoever you're communicating with can look at his/her chart and decode with those rules.)

, Unless you expect your friend to decode each and every message you send him or her without a key, create one. Never have more than one copy per person, otherwise you increase the likelihood that someone else will find the key. You can have preset codes with cryptic names, too. For example, you could name the stacked cipher just created above CSP. (Caesar's cipher, Substitution cipher, Phone cipher.) If you apply rule 5 out of all your rules to this code, then you can add 5 to the name, so it's CSP5. Most likely, a spy won't figure out the names. Just send the code in this format:
Create the ciphers you'll be using.
Apply the first cipher.
Double-check your work.
Apply the next cipher.
Double-check your latest work.
Repeat the last two steps until you've used all the ciphers you want to use.
Add rules.
Make the rule.
Apply the rule.
Make a chart of rules.
Make keys.
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