Exam1ReviewQs - question and the following set of letters:...

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CIS 3362 Exam #1 Review Contest Questions 1) Encrypt "HAVEANICEDAY using the Keyword cipher with the keyword "JUICE", starting at A. Here is the key: Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: JUICEABDFGHKLMNOPQRSTVWXYZ Answer: DJVEJMFIECJY 2) Find the corresponding decryption function for the affine encryption function f(x)=(5x+6)%26 x = (5f -1 (x) + 6) % 26 5f -1 (x) = (x – 6) % 26 21(5f -1 (x)) = 21(x – 6) % 26 f -1 (x) = (21x – 126) % 26 f -1 (x) = (21x + 4) %26 3) Encrypt "CRYPTOGRAPHY" using the multiliteral cipher with the keyword "UIJEC". Here's the encryption grid: U I J E C U A B C D E I F G H I/J K J L M N O P E Q R S T U C V W X Y Z Answer: UJEICEJCEEJEIIEIUUJCIJCE 4) Encrypt "KNIGHTS" using the Vigenere cipher and the keyword "UCF" Plain: KNIGHTS Key: UCFUCFU ------- Answer:EPNAJYM
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5) What is the index of coincidence of the following set of letters: 2 As, 8 Bs, 4 Cs, and 6Ds? IC = 19 5 380 100 380 30 12 56 2 19 20 5 6 3 4 7 8 1 2 = = + + + = + + + x x x x x 6) What is the mutual index of coincidence between the set of letters in the previous
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Unformatted text preview: question and the following set of letters: 6 As, 7 Bs, 3 Cs, and 4 Ds? MIC = 50 13 400 104 400 24 12 56 12 20 20 4 6 3 4 7 8 6 2 = = + + + = + + + x x x x x 7) Find 23-1 mod 73. 73 = 3x23 + 4 , so 4 = 73 3x23 23 = 5x4 + 3, so 3 = 23 5x4 4 = 1x3 + 1, so 1 = 4 3. Now substitute for 3: 1 = 4 (23 5x4), so 1 = 6x4 23. Now substitute for 4: 1 = 6x(73 3x23) 23 1 = 6x73 19x23 Now, consider this equation mod 73: 1 = -19x23 (mod 73) Thus, our desired inverse is -19, which maps to 73 19 = 54. 8) Encrypt "MINNESOTA" with the Playfair cipher with the keyword "KNIGHTS". Use the dummy letter 'X', if necessary. Since we have the double N lining up, we do have to use the dummy letter, so we end up encrypting "MI NX NE SO TA" Here's the playfair encryption grid: K N I/J G H T S A B C D E F L M O P Q R U V W X Y Z Answer: FHIWSPTPSB...
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This note was uploaded on 07/13/2011 for the course CIS 3362 taught by Professor Staff during the Fall '08 term at University of Central Florida.

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Exam1ReviewQs - question and the following set of letters:...

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