Question Paper: Data Compression and Encryption* Question Paper - May 18 - Electronics And Telecomm (Semester 7) - Mumbai University (MU)

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## Data Compression and Encryption* - May 18

### 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.

**1(a)**Discuss the concept of LZ78 with an example.

**1(b)**What is motion estimation? How is it useful for video compression?

**1(c)**Define Euler's totient function. Compute $\phi$(37),$\phi$(49),$\phi$(100).

**1(d)**Define hash function and state its properties.

**2(a)**Consider a source with symbols = {m, n, o, p) with corresponding probabilities {0.4, 0.3, 0.1, 0.2). Using arithmetic coding, determine the output tag for the message "monop". Also, reconstruct the message using this tag.

**2(b)**Draw and explain the working of AES encryption algorithm.

**3(a)**Using RSA algorithm, user X chooses the public key (n=21, e = 5). Compute the private key d of user X. User Y wants to transmit message M=19 to user X in a confidential manner using RSA algorithm, determine the cipher text C.

**3(b)**Draw and explain the working of JPEG image compression standard.

**4(a)**Discuss the concept of $\mu$-law companding. Using $\mu$-law companding, determine the encoded output value for an input audio sample with value (+358). Also, reconstruct to determine the decoded value.

**4(b)**What is Certificate Authority? How is a digital certificate obtained and verified?

**5(a)**What is Intrusion Detection System? Discuss the different techniques of implementing it.

**5(b)**Solve the linear congruent equation for x: 232x + 42 = 48 mod 50.

**5(c)**How is the accumulation of error avoided when using DPCM for image compression?

**6(a)**Draw and explain the working of Key Distribution Center for exchanging secret keys.

**6(b)**Compare statistical and dictionary compression techniques.

**6(c)**What is a one-way trapdoor function? List three one-way trapdoor functions used in cryptography.