Question Paper: Data Compression and Encryption* Question Paper - May 17 - Electronics And Telecomm (Semester 7) - Mumbai University (MU)
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## Data Compression and Encryption* - May 17

### Electronics And Telecomm (Semester 7)

Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question No. 1 is compulsory.
(2) Attempt any three from remaining five questions.
(3) Assume suitable data if necessary, with proper justification.

Q1) Answer the following in brief:

• a) Classify data compression techniques and give example for each 1012

• b) What are one way trap door functions? What is their importance in cryptography?

• c) State:-i) Fermat's little theorem ii) Euler's theorem iii) Chinese Remainder theorem iv) Definition of primitive root. 1046 1047

• d) What do you mean by "auditory masking" and "temporal masking"? 1483

(20 marks)

2(a) A source with alphabet A= {a,b,c,d,e} with probabilities P= {0.15, 0.05, 0.25, 0.35, 0.2} respectively, calculate Standard Huffman code Minimum variance Huffman code Avg length & variance for both codes Draw binary tree for both.
(10 marks) 1011

2(b) What are private key cryptosystems? What are their advantages & disadvantages? Explain DES with neat block diagram.
(10 marks) 1053

3(a) What are dictionary based compression schemes? Explain the LZ-77 technique with an example.
(10 marks) 1025

3(b) Alice and Bob choose p=13 and q=5 as prime numbers for RSA encryption. Alice choose e=7 as public key. Derive her private key. She wants to send plain text 17 to Bob using RSA. Compute the encrypted text and show how Bob will decrypt it.
(10 marks) 1056

4(a) Explain the principle of working of MP-III audio compression standard, with a neat block diagram.
(10 marks) 1029

4(b) What are elliptic curves? Explain the "Elliptic curve Discrete Log" problem and hence explain ECC key exchange algorithm.
(10 marks) 1057

5(a) Explain any one lossless technique for image compression in detail.
(10 marks) 00

5(b) What are digital signatures? Explain any one technique in detail.
(10 marks) 1060

Q6) Write short notes on any two:-

• a) MPEG video compression standard 1036

• b) Hash and MAC functions 1059

• c) Digital Immune System 1068

• d) Diffie-Hellman key exchange 1056

(20 marks)