Solutions to Assignment 2 Barr 2.3: 2, 3a, 3b, 4*, 7, 10* 2. The keywords PRIME MINISTER are to be used to construct a mixed cipher alphabet by columnar transposition. (a) Obtain the cipher alphabet. Using the procedure outlined on Page 85, we obtain the following: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z P A K R Y B L Z I C O M D Q E F U N G V S H W T J X (b) ITISM UCHEA SIERT OBECR ITICA LTHAN TOBEC ORREC T is enciphered as IVIGD SKZRP GIRNV EARKN IVIKP MVZPQ VEARK ENNRK V (c) PFNRK RYRQV RDAPM DGPFN IQKIF MR is deciphered as APREC EDENT EMBAL MSAPR INCIP LE 3. (a) Deciphered message: THREE MAY KEEP A SECRET IF TWO OF THEM ARE DEAD. (b) EDUCATION HAS BECOME A PRISONER OF CONTEMPORANEITY. IT IS THE PAST, NOT THE DIZZY PRESENT, THAT IS THE BEST DOOR TO THE FUTURE.4.* Following the procedure described from pages 85-90, the original plaintext is found to be: FOURSCORE AND SEVEN YEARS AGO OUR FATHERS BROUGHT FORTH ON THIS CONTINENT A NEW NATION CONCEIVED IN LIBERTY AND DEDICATED TO THE PROPOSITION THAT ALL MEN ARE CREATED EQUAL. Keyword: LINCOLN 7. Using the Polybius checkerboard, the deciphered quote reads: A SHORT SAYING OFT CONTAINS MUCH WISDOM. 10. Note that there are 26 possibilities for A, 25 possibilities for B, 24 possibilities for C and so on. Thus there are 26! = 403291461126605635584000000 = 4.03 x 1026 possible substitution keys. The computer takes 10-9 seconds to check one key, so in the worst case scenario where the computer has to go through all 26! possibilities, it would take the computer 4.03 x 1026 keys x 10-9 sec/key = 4.03 x 1017 sec = 1.28 x 1010