# Decipher this message.

REHPA RGOTP YRCAE RAUOY.

Is it a mistake or gobbledygook? Actually, it's a coded message.

Keeping a secret has always been important, and people have devised many ingenious ways to send secret messages. Messages have been coded or have been concealed in tubes, boxes, or the back of paintings.

One unusual way of hiding a message was used in the fifth century B.C. The head of a messenger was shaved, the message was tattooed on the messenger's scalp, and then his hair was allowed to regrow. When the messenger reached his destination, his head was shaved to read the message.

Often there isn't time for a messenger to regrow a head of hair, so cryptographers (people who specialize in coding and decoding messages) devised other ways for sending secret messages.

If you and a friend want to exchange coded messages, you could send a backwards message or use a rail fence cipher or a substitution cipher.

To send a backwards message, reverse the letters and divide the message into "fake" words: ERIPM AVAHT IWNAM WONSA SSORC UOYFI TEGUO YODTA HW?

Your friend decodes the message by reversing the letters, beginning with the last letter: WHAT DO YOU GET IF YOU CROSS A SNOWMAN WITH A VAMPIRE?

To send the answer to this riddle, you tell your friend you'll use a rail fence cipher with two "rails" (or rows) on the fence. The coded answer to the riddle is: FOTIE RSBT.

Your friend decodes the answer by first counting the number of letters (nine letters) and then drawing a grid with nine spaces and two rows. Your friend writes the first letter in the first space of the top row, skips a box, and writes the second letter in the next box, and so on. The answer to the riddle looks like this:

Next your friend sends you a riddle by using a substitution cipher with a key word. The key word you and your friend have chosen is "sleuth." (It's best to choose a key word that doesn't have any repeated letters.) Your friend draws a 26-space grid with two rows and puts the alphabet in its regular order in the top row and in the bottom row puts the key word followed by all the letters in the alphabet that are not in the key word.

Then your friend codes a message by finding each letter of the message in the top row and writing the corresponding letter in the bottom row. Your friend sends you a coded riddle and its answer: WBSQ UK YKR ESGG S MCA CJ QBT LRPBTP? S BTUATBKA.

You decode the message by reversing the process your friend used. You find each letter in the bottom row of the grid and then write down the corresponding letter from the top row. You'll discover that the riddle is: WHAT DO YOU CALL A PIG IN THE BUSHES?

Now try your hand at deciphering the answer to the riddle and the coded message at the beginning of this article.

pg. 6: YOU ARE A CRYPTOGRAPHER.

pg. 7: WHAT DO YOU CALL A PIG IN

THE BUSHES?