← Secret Writing · Lesson 2 of 3
Count the letters
A shift cipher has only 25 possible shifts, so you could try them all. But there is a faster way, first written down by the Arab scholar al-Kindi in the 800s: frequency analysis.
In English text, E is the most common letter. Count the letters in a coded message; the most common one probably stands for E. Work out the shift from there.
In a long coded message, the most common letter is H. What shift was probably used?
A lesson is kept once you've answered the question and written at least 8 words. Nobody grades it; it stays on this device.