Tutorial: One Time Pad

Here's an old tutorial that I've posted in a few places:

(Source)

I suppose I will now explain how One Time Pad encryption works:

Imagine you have a friend (hard to imagine, I know), and you want to send this friend a super secret message at a later date. Say... your friend is moving to another country, but you want to tell him/her where you are going to bury the gold you stole from a bank. But not right now, you need to wait until the heat dies down and the cops stop asking questions.

So, you and your friend agree upon a One Time Pad: a long series of randomly generated alphabet characters.  Once your friend moves and the heat dies down, you want to send a message to your friend about the whereabouts of the gold.

But plaintext would be a really stupid way to tell your friend. Thus, you encrypt it with a similar method used in that picture up there.

Up there, moron.

When you're partner-in-crime gets the message, they decrypt it with a similar method.

But, you're probably wondering why should you go through the trouble of a one time pad?  Well, the answer is simple:  one time pad encryption (if done correctly) cannot be broken.

That is, given infinite processing time, no one can break your encrypted code to get the decrypted message.

Why?

The answer is in the fact that the encryption string is as long as the message. That way the message is secure against usual frequency analysis.  In fact, it is possible to "decrypt" out of the ciphertext any message whatsoever with the same number of characters, simply by using a different key, and there is no information in the ciphertext which will allow [you] to choose among the various possible readings of the ciphertext.

Yay One Time Pad Encryption!