Why shouldn I use a Diceware passphrase shorter than 14 characters?
One way someone might use to find your passphrase is to write a computer program that tries all combinations of characters up to some length. If your Diceware passphrase is very short, such a program would come up with you passphrase eventually. Using a passphrase that is at least 14 characters in length, including the spaces between the words, makes such an attack as difficult as searching all five word Diceware passphrases. By the way, it is very unlikely that the dice will give you a passphrase that short. If you use a four word passphrase, it should be at least 11 characters in length, including the spaces between the words. For six words, at least 17 characters. You could just select another word to make the short passphrase longer, but since the passphrase will consist almost entirely of two letter combinations, and therefore will be very hard to remember, I recommend selecting a new passphrase from scratch. Since such short passphrases are very rare, rejecting them does not mate
