Some words out of an enciphered message. Click one.
Shapes, not letters
Take any word and label its letters in the order they first appear. The first new letter is A, the second is B, and a repeat gets the label it had before.
So NOON is A B B A. So is DEED, and so is SEES. And nothing else in English is, much. A four letter word shaped A B B A has only a handful of candidates, and a substitution cipher does not hide the shape at all.
This is why long words are a gift to a code-breaker. LETTER, COOKIE and BOTTLE all share a shape that almost nothing else has.
Two ways in, working together
Counting tells you which letters are common. Shapes tell you which words they might be in. Together they finish a substitution cipher fast: guess E from the tallest bar, find a three letter word ending in E, try THE, and now you have T and H as well.
And this is exactly what a transposition cipher defeats. If the letters were only moved and not replaced, the shapes are destroyed and the letter counts are untouched — the opposite of a substitution. Which of the two you are facing is the first thing to work out.
What am I looking at? Frequency analysisRead more elsewhere
Longer, harder and written for grown-ups. Worth a look when this page runs out.