M.TECH. DEGREE EXAMINATION Branch: Computer Science and Engineering Specialization : 1. Computer Science and Engineering, 2. Information Systems Model Question Paper - I Second Semester MCSCS 203/ MCSIS 203 COMPUTER SECURITYAND APPLIED CRYPTOGRAPHY (Regular – 2011 Admission onwards) Time: Three Hours Maximum: 100 Marks 1. (a) Explain the model of a conventional cryptosystems. (10 Marks) (b) Briefly define the categories of passive and active security attacks. (5 Marks) (c) What are the two general approaches to attacking a cipher? (10 Marks) OR 2. (a) What is the difference between a block cipher and a stream cipher? (10 Marks) (b) What is steganography? (5 Marks) (c) Distinguish between monoalphabetic and polyalphabetic cipher. (10 Marks) 3. (a) Explain Blowfish. (15 Marks) (b) What is the purpose of S-boxes in DES? (5 Marks) (c) Briefly explain a Group, Ring and a Field. (5 Marks) OR 4. (a) With suitable example explain the RSA algorithm (15 Marks) (b) Explain Diffie-Hellman key exchange. (10 Marks) 5 (a) What is a Message Authentication code? (10 Marks) (b) What is the difference between weak and strong collision resistance? (5 Marks) [P.T.O] (c) Explain S/MIME. (10 Marks) OR 6 (a) What is the purpose of X.509 standard? (10 Marks) (b) Explain digital signature. (10 Marks) (c) What are the principal services provided by PGP (5 Marks) 7 (a) List IPSec services. (5 Marks) (b) Briefly define the principal categories of SET participants. (10 Marks) (c) Sketch IPSec authentication header and explain various fields. (10 Marks) OR 8. (a) List and define three classes of intruders. (5 Marks) (b) Briefly explain SSL architecture. (10 Marks) (c ) Explain the different types of firewalls. (10 Marks)