Koofers

Past Exam for CMSC 414 - CMPTR & NETWORK SECURITY with Shankar at Maryland (UMD)

Exam Information

Material Type:Exam 1
Professor:Shankar
Class:CMSC 414 - CMPTR & NETWORK SECURITY
Subject:Computer Science
University:University of Maryland
Term:--
Keywords:
  • Authenticates
  • Particularly
  • Authentication
  • Convenience
  • Environment
  • No Correlation
  • Initialization
  • Permutation
  • The Message
  • Random Number
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Sample Document Text

CMSC 414 F06 Exam 1 Page 1 of 8 Name:_________________________ _____________________________________________________________________________________ Total points: 40. Total time: 75 minutes. 6 problems over 6 pages. No book, notes, or calculator 1. [14 points] Are n=187 and e=9 valid numbers for RSA. Explain. If you answer yes, obtain the corresponding d. _____________________________________________________________________ Solution There are two requirements:  n must be a product of two primes  e must be relatively prime to f(n) (so that d, which equals e-1 mod-n, exists) First requirement [2 points] n = 187 = 1117. 11 and 17 are primes. So this holds. Second requirement [6 points] Recall that if n =pq where p and q are distinct primes, then f(p q) = (p-1) (q-1) So f(187) = (11-1) (17-1) = 160. e, which equals 9, is relatively prime to 160 (because 9=32 and 160=1016=2524=255) So this requirement holds. Obtaining d ...

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