This set of MCQ(multiple choice questions) focuses on the **Foundations of Cryptography** **NPTEL Week 12 Assignment Solutions**.

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**Assignment answers** - Week 11:
**Assignment answers** - Week 12: Assignment answers

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**Foundations of Cryptography** NPTEL Week 12 Assignment Solutions

**Q1.** For Shamir secret sharing scheme:

a) The correctness holds if the Lagrange’s interpolation is performed over a ring

b) The correctness holds if the Lagrange’s interpolation is performed over the integers

c) The privacy does not hold if the secret is set to be any other coefficient of the sharing polynomial, except the constant term

d) None of these option

**Answer:** d)

**Q2.** Which of the following is/are true for additive secret-sharing?

a) The shares of up to n-1 parties need not be communicated, if the adversary is computationally bounded and if there is a pre-shared, uniformly random and private PRF key between the dealer and every share-holder

b) Irrespective of the kind of setup available, the shares of every share-holder have to be communicated, even if the adversary is computationally bounded

c) The shares of any party need not be communicated, if the adversary is computationally bounded and if there is a pre-shared, uniformly random and private PRF key between the dealer and every share-holder

d) None of these option

**Answer:** a)

**Q3.** Consider the following variant of additive secret-sharing for sharing a n-bit secret among n share-holders P_{1},…,P_{n} where up to n-1 share-holders could be corrupt: to share an n-bit secret s=(s_{1},…,s_{n}), where s_{1},…,s_{n} are the bits of the secret s, the dealer gives party P_{i} the share s_{i}

a) The scheme provides perfect security

b) The scheme provides computational security

c) The scheme is secure provided n is sufficiently large

d) None of these option

**Answer:** d)

**Q4.** For the additive secret-sharing scheme:

a) The operations have to be necessarily performed over a ring

b) The operations have to be necessarily performed over a field

c) The privacy holds against a computationally unbounded adversary

d) The privacy property is guaranteed only if the adversary is computationally bounded

**Answer:** c)

**Q5. **Which of the following is/are true for Shamir secret-sharing?

a) The shares of up to t parties need not be communicated, if the adversary is computationally bounded and if there is a pre-shared, uniformly random and private PRF key between the dealer and every share-holder

b) Irrespective of the kind of setup available, the shares of every share-holder have to be communicated, even if the adversary is computationally bounded

c) The shares of any party need not be communicated, if the adversary is computationally bounded and if there is a pre-shared, uniformly random and private PRF key between the dealer and every share-holder

d) None of these option

**Answer:** a)

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