About the "Unbreakable Code"

by oddballz194

Ciphers are methods of encoding information by substituting symbols for one another. One of the earliest ciphers is the simple substitution cipher, which was used by, among others, Julius Caesar. The Box Code, discussed in the article entitled "Unbreakable Code?", is just a permutation on the simple substiutution cipher.

The fact is that it is trivial to crack such a cipher. One need only write a program that uses a 2x2 block as the substitution source, and check the letters in the message. Here's the method:

1. Read the first two letters.
2. Search the 2x2 boxes, and if both letters are in the box, then the letter in the upper-left corner is the letter of the message.

Note that although this method is for only the simplest case, it can be extended to the other methods used by the author of the article. (In fact, we have one essential piece of information by the fact that it is the box code -- the real letter is in the box selected if both letters are in the box!) It is fairly simple to check all four letters randomly, as it is unlikely that more than one combination of letters from the set of boxes will result in English words (or sensible words in any language). This is actually a simplified and EASIER to crack code than the simple substitution cipher, in a way.

There is only one unbreakable code. It is called the One Time Pad. To use it, we need two keys. One key is the same regardless of message: You simply assign numbers to the letters. Here's one example:

a-1 b-2 c-3 d-4 e-5 f-6 g-7 h-8 i-9 j-10 k-11 l-12
m-13 n-14 o-15 p-16 q-17 r-18 s-19 t-20 u-21 v-22
w-23 x-24 y-25 z-26

Now create the pad, which is the other key. To do this, simply use a random string of digits. They are usually square, like so:

914 894 237 414 507
733 193 129 394 912
903 478 284 271 327
549 854 485 456 938
495 638 585 203 485

I will give an example of encoding a message, which will describe the message. For example, to encode a message "Let's go out", we do the following:

The Letter L is 12 in our first key, so we add 12 to 914 to get 926. E is 5, so we add 5 to 894 to get 899. Continuing, we get:

926 899 257 433 514
748 208 150 414

To decode this message, we need BOTH keys. Presumably you gave the pad itself to your intended recipient already. All he has to do is take the coded message and subtract the numbers from the pad. In this case:

926-914=12
899-894=5
257-237=20

...And so on. When finished, he gets:

12 5 20 19 7 15 15 21 20

Now decoding, it becomes: letsgoout

This code is impossible to break without the pad itself. As a result, once the message is passed, you should destroy the pad used for that message. When decoding a message, the pad used to decode it should be destroyed. That way, no two messages are encoded with the same pad, and it becomes impossible to break. This code has been used, with some variations, by the intelligence services of several nations, including the USA and the USSR (back when it existed). It is mathematically impossible to break since without the pad there is no way to know which letter corresponds with a coded value.

Have fun!