Then the textbooks often define the security like this: If for all PPT adversary A, there exists a negligible function $\mathsf{negl}$ satisfies $\Pr[\mathsf{Exp}_{A,\Pi}(\lambda) = 1] \leq 1/2 + \mathsf{negl}(\lambda)$, then we say $\Pi$ is a indistinguishable scheme...

2013年11月8日 · In order to be indistinguishable with respect to multiple messages, wouldn't the scheme need to be nondeterministic? How would this then possibly be vulnerable to an adaptive CPA?

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2025年1月1日 · But how can I use this bound to prove that the sum is indistinguishable from uniform? I was trying to perform some kind of reduction on the fact that $\text{Enc}_K(\cdot)$ produces independent and uniformly indistinguishable $\text{Enc}_K(X)$ and $\text{Enc}_K(Y)$, but without success. $\endgroup$ –

2024年12月20日 · CONSTRUCTION 3.17 Let G be a pseudorandom generator with expansion factor l. Define a private-key encryption scheme for messages of length l as follows: • Gen: on input 1^n, choose uniform k ∈ {0, 1}^n and output it as the key. • Enc: on input a key k ∈ {0, 1}^n and a message m ∈ {0, 1}^{l(n)}, output the ciphertext c := G(k) ⊕ m.

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2015年5月17日 · I can't think of any simple example of probability ensembles which are computationally indistinguishable, except trivially if they are identical or just assumed to be indistinguishable. Indeed, constructing probability ensembles which are non-trivially computationally indistinguishable is in a way what cryptography is all about...

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2014年4月1日 · $\begingroup$ There could conceivably be a commutative block cipher whose outputs for a given key on an entry-wise unpredictable list of inputs are indistinguishable from being independently-and-uniformly distributed. $\hspace{.42 in}$ $\endgroup$

2018年6月21日 · No, a PRG doesn't provide indistinguishability when encrypting multiple distinct messages. Indistinguishability always refers to random.