# MD_NS_II - (e) What requirements must a public key...

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Birla Institute of Technology & Science, Pilani Work-Integrated Learning Programmes Division First Semester 2009-2010 Mid-Semester Test (EC-1 Regular) Course No. : SS ZG513 Course Title : NETWORK SECURITY Nature of Exam : Closed Book Weightage : 40% Duration : 2 Hours Date of Exam : 29/08/2009 (FN) Note: 1. Please follow all the Instructions to Candidates given on the cover page of the answer book. 2. All parts of a question should be answered consecutively. Each answer should start from a fresh page. 3. Mobile phones and computers of any kind should not be used inside the examination hall. 4. Use of any unfair means will result in severe disciplinary action. Q.1. Answer the following: (a) What is the difference between passive and active security threats? (b) List important design considerations for a stream cipher. (c) Why is it not desirable to reuse a stream cipher key? (d) What is the difference between Rijndael and AES?
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Unformatted text preview: (e) What requirements must a public key cryptosystems fulfill to be a secure algorithm? [10] Q.2. Describe the advantages and disadvantages of symmetric and asymmetric key cryptography. [5] Q.3. What is the difference between link and end-to-end encryption? [5] Q.4. Alice meets Bob and says Rjjy rj ts ymj xfggfym. Bj bnqq inxhzxx ymj uqfs . If she is using Caesar Cipher, what does she want to convey? [5] Q.5. Given a plain text alphabet G, using the RSA algorithm and the values as E=3, D=11, and N=15, find out what this plain text alphabet encrypts to and verify that upon decryption it transforms back to G. [8] Q.6. What is the source of presence of the Weak-keys, Semi-Weak-keys and Possibly-Weak-keys in the DES? Is it possible to implement DES so that this problem could be effectively handled, if at all? Explain in detail. [7] ********* No. of Pages = 1 No. of Questions = 6...
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## This note was uploaded on 02/05/2012 for the course NETWORK SE SS ZG513 taught by Professor Raj during the Spring '11 term at Birla Institute of Technology & Science, Pilani - Hyderabad.

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