NPTEL Foundations of Cryptography Week 2 Assignment Answers 2025
1.
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2.
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3. Suppose we want to execute OTP encryption scheme over message space M={0,1}ℓ+1 but with key-space K={0,1}ℓ . For this, to encrypt an (ℓ+1) -bit message using an ℓ -bit random key k, the encryption algorithm picks an additional random bit x and outputs the ciphertext c=m⊕(k∥x).
- The adversary will not learn any information about the underlying message
- The adversary can learn something about the underlying message
- The scheme satisfies correctness property without any error
- The scheme satisfies the correctness property except with probability ½
- None of these
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4.
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5. Difference between perfect security and semantic security involves one or more of the following:
- Bounds on how long the adversary can run the experiment
- In the respective indistinguishability experiment, adversary has the exact same probability of success
- Bounds on computational capabilities of the adversary
- None of the above
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