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Shifty Caesar.


Julius Caesar might have sent this message to his generals. Caesar was a great warrior and leader. He was also a worrier. But instead of just worrying, Caesar got shifty.

Caesar worried his plans and messages would fall into enemy hands. Using ciphers, Caesar changed his messages into something his enemies could not read. He replaced each letter with a different letter or symbol. The key was to know how the letters had been changed. Only those who knew the key could read Caesar's secret messages.

Caesar used a special cipher during the Gallic Wars. Caesar's Roman army was fighting to take over Gaul, a part of Europe that is France, Belgium, and Switzerland today. One winter, enemies surrounded the camp of Cicero, one of Caesar's generals.

Cicero sent messages to Caesar, pleading for help. Caesar began gathering troops to come to the rescue. Caesar wrote to Cicero, telling him to not lose hope. Help "will quickly be there," he 'wrote. But Caesar didn't want the Gauls to know he was coming, so he wrote his message in cipher. He replaced the usual Latin letters with Greek letters. Cicero had the key. He knew how to read the secret message. Caesar and his troops arrived, and the Romans won the battle. The Greek cipher was a success.

Caesar created another cipher that now bears his name. Suetonius, Caesar's biographer, wrote about Caesar's famous cipher. "If [Caesar] had anything [private] to say, he wrote it in cipher." Suetonius described the cipher, now called the "Caesar shift" or "Caesar cipher."

To create this cipher, Caesar shifted the letters in the alphabet three places to the right. An "a" became a "d," a "b" became an "e," and so on. Caesar wrapped around to the start of the alphabet when he reached "x," replacing it with "a." Readers decoded messages by shifting the letters three places to the left.

If you were a Roman general, you would have known Caesar's key. You would have read his secret messages. You would have been shifty like Caesar.

illustrated by Harvey Hirsch



Return to Rome
Working with the Caesar Shift

Plaintext      a   b   c   d   e   f   g   h   i   j   k   l   m

Ciphertext:    D   E   F   G   H   I   J   K   L   M   N   O   P

Plaintext      n   o   p   q   r   s   t   u   v   W   x   Y   z

Ciphertext:    Q   R   S   T   U   V   W   X   Y   Z   A   B   C

This table shows the letter mapping of a Caesar shift. To create a
message, Caesar replaced each real letter in the message (the
plaintext letter) with the letter below it (the ciphertext letter).

Using this cipher, Caesar might have written the following message.
You know the key. You can decode it.
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Title Annotation:Julius Caesar
Author:Slingerland, Janet
Publication:Fun For Kidz
Geographic Code:1USA
Date:Sep 1, 2013
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