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Say we modify CBC-MAC to incorporate a random IV. So authentication of a 1-block message m using a block cipher F and key k is done by choosing a uniform IV and outputting the tag IV,Fk(IV⊕m). Verification is done in the natural way. Say this scheme is used with an 4-byte block cipher, and an attacker sees the tag 0x01 01 01 01 05 06 07 08 on the message 0x 00 00 01 01. Which of the following will be a valid message/tag pair?

If we encrypt the message 0xAF C0 4D using the one-time pad and key 0xC9 2B 39. What is the resulting ciphertext?

Which of the following is a setting in which a pseudorandom generator could be applied?

What is the size of key space |K| for a shift cipher, considering the message space as English alphabets, and encryption algorithm as Enc​(m)=(m+shift)mod 26?

What is the value (in decimal) of 0x48?

Which of the following problems is hard if the RSA assumption holds? In all the below, N is a product of distinct, large primes p and q, and e is relatively prime to ϕ(N).

Let G be a function mapping n-bit inputs to 2n-bit outputs. Which of the following is true of the pseudo one-time pad encryption scheme based on G?

What is the size of key space |K| for a byte-wise shift cipher, considering the message space as English alphabets, and encryption algorithm as Enc​(m)=(m⊕k)?

In which of the following settings is naive application of private-key cryptography applicable? (Check all that apply.)

3-1 mod 7 = ? Alternatively, what is the inverse of 3 mod 7 on multiplication?