This set of MCQ(multiple choice questions) focuses on the **Foundations of Cryptography** **NPTEL Week 6 Assignment Solutions**.

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**Foundations of Cryptography** NPTEL Week 6 Assignment Solutions

**Q1.** Choose the incorrect option(s) from the following:

a) (R,× ) is a group

b) (R-{0},+) is a group

c) (Z – {0}, +) is an abelian group

d) (R -{0} ,× ) is a group

**Answer:** a), b), c)

**Q2.** Select the incorrect option(s) for the Merkle-Damgård transformation:

a) It employs a multi-stage approach and used in many popular hash algorithms like MD5, SHA256

b) This construction will always add a padding to the message which depends upon the length of the message

c) The initial vector (IV) used in this construction can be randomized

d) The transformation is a deterministic function of the input

**Answer:** c)

**Q3.** Given H is a collision-resistant hash function. Then which of the following is/are false?

a) The function H_1 (x)≝H(x)||H(x) is not collision-resistant

b) The function H_1 (x)≝H(x)||H(x) is collision-resistant

c) The function H_2 (x)≝1||H(x) is collision-resistant

d) The function H_2 (x)≝1||H(x) is not collision-resistant

**Answer:** a), d)

**Q4.**

Neither the construction in part (a), nor the construction in part(b) is secure

The construction in part (a), as well as the construction in part(b) are secure

**Answer:** a)

**Q5. **Let *F:*{0, 1}^{n} X {0, 1}^{n} be a keyed function and let *H: M* => {0, 1}^{n} be a function, where M = {0, 1}^{≤l}, where l is some polynomial function of the security parameter. Then consider the keyed function *F’*: {0, 1}^{n} X M => {0, 1}^{n}, where *F’*_{k}(m) = *Fk(H(m)). *Which of the following is/are true?

a) If F is a secure PRF, then F’ is a secure PRF

b) If H is collision-resistant, then F’ is a secure PRF

c) If F is a secure PRF and H is collision-resistant, then F’ is a secure PRF

d) Even if F is a secure PRF and H is collision-resistant, the function F’ need not be a secure PRF

**Answer:** c)

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Rohan SharmaBro plz upload week-7, today is last date.

Chacha hamare VidhayakAssignment 7 please quick

NaveenBro today is the last date for week7…pls upload answers

YashAnswers added for Week 7. Check them now! 🙂

Chacha hamare VidhayakWhere is our hero? Help us man

Yash🙂

Answers added for Week 7. Check now and complete the assignment before due.