# Chapter28 - CHAPTER 28 Network Security Exercises 1...

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1 CHAPTER 28 Network Security Exercises 1. Substitute the character that is 4 characters down. For example, X is 4 characters down from T and L is 4 characters down from H. The encrypted message is 3. Using statistics, we can find 5. a. 65 66 67 65 68 69 70 71 72 b. 0 1 2 0 3 4 5 6 7 c. 00000 00001 00010 00000 00011 00100 00101 00110 00111 7. N = 19 × 23 = 437 ( p 1)( q 1) = 396 Select an e such that it is relatively prime to 396. An e = 5 satisfies the condition. Now we need a d such that (5 × d ) mod 396 = 1. Solve the equation 396 y = 5 d 1, with y an integer. We need a y that when multiplied by 396, the ones’ digit is 4 or 9 so that it is evenly divisible by 5. If y is 4, then d = 317. XLMW MW E KSSH IBEQTPI ENCRYPTION IS LIKE ENCLOSING A SECRET IN AN ENVELOPE

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SECTION 2 9. ( 1 × 227) mod 100 = 27 (27 × 227) mod 100 = 29 (29 × 227) mod 100 = 83 (83 × 227) mod 100 = 41 (41 × 227) mod 100 = 7 ( 7 × 227) mod 100 = 89 (89 × 227) mod 100 = 3 ( 3 × 227) mod 100 = 81
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Chapter28 - CHAPTER 28 Network Security Exercises 1...

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