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Code No: RR410504 Set No. 1
IV B.Tech I Semester Regular Examinations, November 2007NETWORK SECURITY AND CRYPTOGRAPHY
(Computer Science & Engineering)Time: 3 hours Max Marks: 80
Answer any FIVE QuestionsAll Questions carry equal marks
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1. (a) What is it importance to study the Feistel cipher? [8]
(b) Which parameters and design choices determine the actual algorithm of aFeistel cipher? [8]
2. Explain the process of encryption and decryption in IDEA algorithm. [16]
3. List four general categories of schemes for distribution of public keys. [16]
4. (a) Explain Chinese Remainder Theorem.
(b) State and prove Euler’s theorem?
(c) Using Fermat’s theorem, find 201 mod 11. [5+5+6]
5. (a) List requirements for a Hash Function.
(b) What basic arithmetical and logical functions are used in SHA-1? [6+10]
6. (a) What is R64 conversion?
(b) Why is R64 conversion useful for an e-mail application?
(c) Why is the segmentation and reassembly function in PGP needed? [4+6+6]
7. (a) Give examples of applications of IPSec.
(b) What services does IPSec provide? [8+8]
8. Write notes on
(a) Viruses
(b) Worms
(c) Bacteria [6+6+4]
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Code No: RR410504 Set No. 2
IV B.Tech I Semester Regular Examinations, November 2007NETWORK SECURITY AND CRYPTOGRAPHY
(Computer Science & Engineering)Time: 3 hours Max Marks: 80
Answer any FIVE QuestionsAll Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) What are differences between a block cipher and a stream cipher? [8]
(b) Explain various modes of operations of block ciphers. [8]
2. Explain the process of encryption and decryption in IDEA algorithm. [16]
3. (a) Explain public key Crypto Systems. [6]
(b) Explain in detail about Euclid’s Algorithm. [5]
(c) Give a brief account on Random number Generation. [5]
4. (a) Explain in detail about Euclid’s Algorithm.
(b) Determine gcd(1970,1066). [8+8]
5. (a) What is a difference between little-endian and big-endian format?
(b) What basic arithmetical and logical functions are used in MD5? [6+10]
6. (a) What is R64 conversion?
(b) Why is R64 conversion useful for an e-mail application?
(c) Why is the segmentation and reassembly function in PGP needed? [4+6+6]
7. Write note on Encapsulating security payload. [16]
8. (a) what information used by a typical packet-filtering router?
(b) What are some weaknesses of a packet-filtering router?
(c) What is the difference between a packet-filtering router and a stateful inspec-tion firewall? [8+4+4]
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Code No: RR410504 Set No. 3
IV B.Tech I Semester Regular Examinations, November 2007NETWORK SECURITY AND CRYPTOGRAPHY
(Computer Science & Engineering)Time: 3 hours Max Marks: 80
Answer any FIVE QuestionsAll Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) What is it importance to study the Feistel cipher? [10]
(b) What is the purpose of the S-boxes in DES? [6]
2. (a) List the characteristics of advanced block ciphers. [8]
(b) What are the differences between RC5 and RC2? [8]
3. (a) Explain Diffie-Hellman Key Exchange in Elliptic curve cryptography?
(b) Explain the process encryption and decryption in Elliptic curve cryptography?[8+8]
4. (a) Explain Miller-Robin test algorithm.
(b) Explain Chinese Remainder Theorem . [8+8]
5. (a) What is the difference between weak and strong collision resistance?
(b) What is the role of a compression function in a hash function? [6+10]
6. (a) What is R64 conversion?
(b) Why is R64 conversion useful for an e-mail application?
(c) Why is the segmentation and reassembly function in PGP needed? [4+6+6]
7. Write note on Encapsulating security payload. [16]
8. Write notes on
(a) Trapdoors
(b) Logic bomb
(c) Trojan horses [5+5+6]
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Code No: RR410504 Set No. 4
IV B.Tech I Semester Regular Examinations, November 2007NETWORK SECURITY AND CRYPTOGRAPHY
(Computer Science & Engineering)Time: 3 hours Max Marks: 80
Answer any FIVE QuestionsAll Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. This problem provides a numerical example of encryption using a one-round versionof DES. We start with the same bit pattern for the key and plain text, namely,In hexadecimal notation 0 1 2 3 4 5 6 7 8 9 A B C D E F
Inbinary notation: 0000 0001 0010 0011 0100 0101 0110 01111000 1001 1010 1011 1100 1101 1110 1111
(a) Derive K1, the first - round subkey.
(b) Derive L0, R0
(c) Expand R0 to get E[R0]
(d) Calculate A=E[R0] ⊕ K1.
(e) Group the 48-bit result of (d) into sets of 6 bits and evaluate the correspondingS-box substitutions.
(f) Cancatenate the results of (e) to get a 32-bit result,B.
(g) Apply the permutation to get P(B).
(h) Calculate R1=P(B) ⊕ L0
(i) write down the cipher text. [16]
2. (a) List the characteristics of advanced block ciphers. [8]
(b) What are the differences between RC5 and RC2? [8]
3. (a) What is an Elliptic Curve? [4]
(b) What is the Zero point of an elliptic curve? [2]
(c) Explain the process encryption and decryption in Elliptic curve Cryptography?[10]
4. (a) Define a Groups, a Rings and a Fields?
(b) Construct Additive table and Multiplicative table for GF(7)? [6+10]
5. Define digital Signature. Explain its role in network security. [16]
6. (a) What is R64 conversion?
(b) Why is R64 conversion useful for an e-mail application?
(c) Why is the segmentation and reassembly function in PGP needed? [4+6+6]
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Code No: RR410504 Set No. 4
7. (a) List and briefly define the business requirements for secure payment processingwith credit cards over the Internet.
(b) List and briefly define the principal categories of SET participants. [8+8]
8. Write notes on
(a) Viruses
(b) Worms
(c) Bacteria [6+6+4]
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