Questions tagged [chosen-plaintext-attack]

Question 1

I'm working on a problem where an encryption scheme like OTP leaks the r-th bit of the key each query where r is a random integer. If an attacker can do an infinite number of queries before the ...

Question 2

I encountered the following question: Prove that given a weak PRF $F:\{0,1\}^*\times\{0,1\}^*\mapsto\{0,1\}^*$ that doubles the length of each input (that is, if ...

Question 3

This question comes from exercise 4.20 of Boneh and Shoup's "Graduate Course in Applied Cryptography [ver. 0.6]:" Let $\pi: X\rightarrow X$ be a permutation, where $X=\{0,1\}^n$. Recall that ...

Question 4

I am taking the Online cryptography course by Dan Boneh. There is a segment that talks about CPA (Chosen Plaintext Attack) Security. I understand that to prevent CPA, we want the encryptions of the ...

Question 5

5.12 (Repeating ciphertexts). Let $\mathcal{E} = (E, D)$ be a cipher defined over $(\mathcal{K}, \mathcal{M}, \mathcal{C})$. Assume that there are at least two messages in $\mathcal{M}$, that all ...

Question 6

Now we have a stream cipher algorithm that works by using a series of obfuscation and diffusion functions to obtain a highly secure key stream, thereby using plaintext XOR key stream to obtain highly ...

Question 7

Let $(\operatorname{Gen}_1, \operatorname{Enc}, \operatorname{Dec})$ be a CPA-secure (IND-CPA) encryption scheme, and $(\operatorname{Gen}_2, \operatorname{Mac},\operatorname{Vrfy})$ be an ...

Question 8

In the following problem: Prove that the following modifications of basic CBC-MAC do not yield a secure MAC (even for fixed-length messages): (b) A random initial block is used each time a message ...

Question 9

Typically a deterministic encryption scheme is characterized by the lack of randomness: a message $m$ will alawys be encrypted to the same ciphertext $c$. A stateful encryption scheme keeps track of a ...

Question 10

I'm going through Katz and Lindell, currently at the part where they introduce pseudorandom permutations, and I was wondering this: given a PRNG, could we construct a CPA-secure scheme as follows? ...

Question 11

It seems like c2 and c3 kinda reveal something but I cannot put my finger on how exactly we can get it. Edit:

Question 12

Proving CPA security using a PRG in place of a PRF I was reading this question, and was wondering what will happen if the pseudorandom generator $G$ is not known publicly (only known to the sender and ...

Question 13

Historical question as BEAST is mitigated in TLS 1.1 and earlier TLS is deprecated. BEAST is a chosen plaintext attack, possible in web browsers because cross-origin requests have cookies ...

Question 14

I am reading papers about homomorphic encryption recently. To my knowledge, all of them opts for the Left-or-Right security i.e. distinguish between $M_0$ and $M_1$ given $\mathcal{E}_K(M_b)$ for $b \...

Question 15

In Gentry's paper "Practical Identity-Based Encryption without Random Oracles", I have a little difficulty understanding the security proof part. The paper claims that in the Challenge phase:...

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Questions tagged [chosen-plaintext-attack]

In the IND-CPA game, is there an upper bound on the number of queries? [closed]

Building symmteric-key encryption from a weak PRF

Insecure variants of Even-Mansour

CPA Security: Does there exist a ciphertext shared by 2 or more plaintexts in randomized encryption

Why CPA-secure implies with overwhelming probability, there will be no repeated ciphertext?

Chosen-plaintext attack on Stream cipher

Is this CPA-secure encryption with EUF-CMA MAC scheme IND-CCA secure?

Prove that this Modified CBC-MAC is not secure

Proving that deterministic and stateless encryption scheme cannot achieve indistinguishability of multiple encryptions

Can we construct a CPA-secure scheme with a PRNG and a random key?

Prove that this RSA based encryption scheme is not IND-CPA secure

Can we construct a CPA-secure scheme using a PRG?

Preventing BEAST by using authorisation header instead of cookies

Real-or-Random Security (IND$-CPA) for Homomorphic Encryption?

Question about Security proof of Gentry's Anonymous IBE

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