Unformatted text preview: cipher text blocks. Show that if an error occurs in C j , then this only affects two blocks for decryption. Which two blocks? [5] Q.3 Using Extended Euclid method find the smallest positive integer X such that, . 73 mod 4 31 = • X [8] Q.4 RSA problem: [4 + 2 +2 = 8] Let p = 11, q = 13 and e =7. (a) Find d (b) Encrypt the message 99. (c) Using two prime numbers p and q that are close to each other in value is a bad idea for RSA. Q.5 In the round key expansion procedure AES uses the 8bit constants Ci, i = 1, 2, 3,…. .,30 that can be computed as Ci = 2 i1 In polynomial arithmetic modulo m(x) = x 8 + x 4 + x 3 + x + 1, that is, in Galois field GF(2 8 ) with polynomial m(x). Compute C8, C9 and C16. [10] Q.6 Explain the following [3] a. Factoring Problem b. Timing Attacks ******** No. of Pages = 1 No. of Questions = 6...
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 Spring '11
 raj
 Cryptography, Encryption, Prime number, Plain text, Pilani Distance Learning, cipher text blocks

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