Math for Liberal Studies – Fall 2007 Dr. Hamblin

Chapter 17: Transposition Ciphers Encode and decode the following messages using the methods presented in class.

1. Encode the message “WARNING AMBUSH AHEAD” using the Rail Fence cipher and four rails.

2. Decode the message “YAOEP LWGOH VCMLT DRBET OPWUE PEOMX” using the Rail Fence cipher and three rails.

3. Encode the message “MEET ME FOR LUNCH AT NOON” using a Route cipher. Write the plaintext in four columns of five letters, start at the lower right hand corner and spiral inwards, counter-clockwise.

4. The message “TSO EAA BYD ITX DUT DHW LRI HPB MSR UOI” was encoded using a Route cipher. The plaintext was written in columns of three letters, and the route started in the upper left and proceeded clockwise. Decode the message. Math for Liberal Studies – Fall 2007 Dr. Hamblin

The next two problems use a Bifid cipher with the following Polybius square.

1 2 3 4 5 1 A B C D E 2 F G H I K 3 L M N O P 4 Q R S T U 5 V W X Y Z

5. Encode the message “THE BROWN FOX JUMPS OVER THE DOG” using the Bifid cipher.

6. Decode the message “BGAHF TDADW QTOXW LKVO” using the Bifid cipher.

7. The message “TLSTR SPHXR ROAEM ROSKP ILDOY IK” was encoded using a Bifid cipher and then a Rail cipher with 3 rails. Decode the message.

Solutions 1. WGHAN ASADR IMUHA NBE 2. YOU HAVE COMPLETED PROBLEM TWO (XPGW) 3. NOONT UEMEE TMLAH CNFOR 4. THIS PROBLEM WAS HARD BUT YOU DID IT (X) 5. RASXH WSOPD RAMSW IHDOW XQWSY R 6. BIFID CIPHERS ARE EASY 7. USING TWO METHODS IS MORE SECURE