How Three-square works

Three-square uses three keyed 5 by 5 squares. Each pair of message letters becomes three ciphertext letters. The middle letter comes from the third square and carries most of the information, while the outer two can be any letter from the right column or row of the first two squares. Because the encoder picks those freely, the same message can be written many ways, which hides repeated pairs.

To decode, enter the three keywords. The ciphertext must come in groups of three letters.