The Solitaire cipher - Superstruct Instructables series

Step 3 Writing and preparing your cleartext message

First off, in order to encrypt a message, you need to have a message to encrypt. Given the time it takes to encrypt text with Solitaire and the level of security it offers, Bruce Schneier suggests that the longest messages should be 2000 characters long. This can be a little short for what you have to say so don't hesitate to use slang or abbreviations. Make sure that your recipient will understand what you mean, though !

Once this is done, it's time to prepare your message for encryption. Encrypting a message doesn't change either words' length or message punctuation, both of which can be indications as to what words you've used in your messages. In order to prevent such an attack - called the "probable word attack" - we're going to apply a few changes to your message.

First, we're going to remove ALL the punctuation in your message. Full stops, commas, etc...Just remove them all.

Second, we're going to take care of the length of the words used. You're going to divide your message's characters in small groups of 5 letters. If you have extras, use the letter X. For example, a short message saying "Do not go" would turn into "DONOT GOXXX".

There's nothing really special about using groups of 5 letters - it's just a convention. In the same way, you'll notice we turned the letters into caps - this too is a convention to differentiate more conveniently cleartext from ciphertext. It also takes care of removing all indication of where a sentence starts or finishes. Neat, is it not ?

Now that we're done, let's move to the next step : preparing the decks !