Question Paper: Data Compression and Encryption* Question Paper - May 16 - Electronics And Telecomm (Semester 7) - Mumbai University (MU)
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## Data Compression and Encryption* - May 16

### 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 wherever necessary with proper justification.

Q1) Answer the following (Any five)

• a) What are the measures of performances for lossy and lossless compression techniques? 1012

• b) Illustrate the worst cast in LZ-77 dictionary compression technique. 1025

• c) What is "frequency/auditory masking temporal mashing"? 1483

• d) Which redundancies are exploited in JPEG lossy standard? Which are the processes using these redundancies?

• e) State fermat's little theorem(FLT) and Euler's theorem. Illustrate with an example how FLT can be used to find modular inverse. 1046

• f) Using modular arithmetic and theorems, prove that decrypted text is same as plain text in the RSA algorithm. 1055

• g) What do you mean by "confusion" and "diffusion"? Which components are used in ciphers to introduce confusion and diffusion?

(20 marks)

2(a) Generate a binary tag using arithmetic coding techniques for the sequence: a b a c a b b

symbol count
a 37
b 38
c 25

(10 marks) 1011

2(b) Perform LZW dictionary compression on the following text string: wabba-wabba-wabba-wabba-woo-woo-woo-woo Initial dictionary:

Index 1 2 3 4 5
Entry - a b o w

(10 marks) 1011 1026

3(a) Explain MP-III audio compression standard with a neat block diagram.
(10 marks) 1029

3(b) What are different approaches for compressing an image? Explain JPEG-LS standard.
(10 marks) 00

4(a) Explain double DES and the need for it. Also explain the "meet-in-the-middle" attack.
(10 marks) 1043

4(b) Explain any one digital signature algorithm in detail.
(10 marks) 1060

5(a) Encrypt the plain text 63 using RSA algorithm which uses prime numbers p=7 and q=11. The public key e=13. Verify that the decrypted text is same as the plain text.
(10 marks) 1054

5(b) Alice chooses her private key x=3 and Bob chooses y=6. If both of them use the primitive root g=7 for prime p=23, what is the key exchanged between Alice and Bob using diffie. Hellman Key exchange?
(10 marks) 1056

Q6) Write short notes on two.

• a) Adaptive Huffman coding 1011

• b) H.264 encoder-decoder 1038

• c) Eliptic curve cryptography 1057

• d) Intrusion detection system

(20 marks) 00