Secure PRGs and PRFs Relationship Quiz

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What can be constructed using secure PRFs and vice-versa?

Random number generators
Secure PRGs (correct)
Secure encryption algorithms
Cryptographically insecure functions

In the context of computing the square root of x^2, what can be learned with only probability 1/2?

Both +x and -x as roots
The sign of exact x (correct)
The square root of x^2
The exact x

Which of the following is true about single message and multi-message CPA-security?

They have no relationship
Single message CPA-security is stronger
Multi-message CPA-security is stronger
They are equivalent (correct)

How can a secure PRF be constructed from a PRG using the tree-construction?

By fixing the input of the function to always 0 (B) Signup and view all the answers

What is a requirement for the length of plaintext in CBC mode encryption?

It should be a multiple of the block length (A) Signup and view all the answers

What is a characteristic of the stateful variant of Counter mode compared to OFB mode?

Secure in Counter mode, insecure in OFB mode (A) Signup and view all the answers

Which of the following is a characteristic of a secure PRG?

The outcome of the PRG is computationally indistinguishable from a true random generator (D) Signup and view all the answers

Which statement about PRGs is false?

A computationally unbounded adversary can determine the seed (C) Signup and view all the answers

What is the primary purpose of a Pseudo-Random Generator (PRG)?

To provide security against computationally bounded adversaries (A) Signup and view all the answers

Why is the output of a PRG considered deterministic?

Because it relies on the seed and a deterministic function (D) Signup and view all the answers

In what way does a PRG aim to overcome the limitations posed by perfect security?

By allowing encryption of long messages with short keys (A) Signup and view all the answers

What does an 'efficient' adversary refer to in the context of cryptographic schemes?

An adversary with almost infinite computational resources (C) Signup and view all the answers

Which of the following is a secure PRG according to the text?

G1 (s) = G(s1 ) ⊕ G(s2 ), where s = s1 ||s2 , and each si ∈ {0, 1}n (B) Signup and view all the answers

What is the probability distribution of G3 (s) in relation to a true random number generator?

Always all zeros (C) Signup and view all the answers

Why is G2 not considered a secure PRG according to the text?

First and second half of the output are the same (D) Signup and view all the answers

What does G4 do with the parity bit of s in relation to a secure PRG?

Appends it to the output (C) Signup and view all the answers

In the context of PRGs, why is XOR of two random/pseudorandom strings significant?

Produces another random/pseudorandom string (D) Signup and view all the answers

What is the significance of concatenation operation in the context of secure PRGs?

Creates predictable patterns (B) Signup and view all the answers