# Questions tagged [indistinguishability]

Ciphertext indistinguishability is property of randomised encryption schemes where it is computationally infeasible to tell if two ciphertexts are encryptions of the same plaintext.

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### How to explain indistinguishability obfuscation (iO) to my grandmother?

At the risk of oversimplification, how do I explain indistinguishability obfuscation (iO) to my grandmother?
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### Is it necessary for a round function $F$ in a Feistel cipher to be pseudorandom?

I stumbled across this question where the questioner asked for specific requirements for the round function $F$ in a Feistel network so that the construction is secure. The answer explained that a ...
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### Noise flooding with Renyi divergence

According to this question, I found papers that deal with noise flooding with Renyi divergence. However, the answer is still unclear to me on how to use Renyi divergence on the noise flooding ...
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The Cryptography made simple (page 207, under Fig 11.12)(Nigel Smart) say that adversary's advantage of IND-PASS Game is $Adv1 = 2\times|Pr[b=b']-\frac{1}{2}|$. The reason for multiplying by 2 is to ...
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### RLWE like problem

Assume we have the polynomial space $R_q$ defined as $R_q = Z_q/(X^n + 1)$. Additionally, we define the error distribution $\chi$ as a discrete centred Gaussian bounded by $B$. Let $s \gets R_q$ be a ...
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### Are semantic security and indistinguishability equivalent for symmetric key cryptosystems?

I've seen a lot written about how, in the context of public key cryptosystems, these definitions are equivalent. Is the same true of symmetric key cryptosystems? If so, what are the precise statements ...
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### How to achieve $d-$privacy considering some secrets?

We have a set of secrets $S = \{x_1, x_2, \dots, x_n\}$ known to an adversary. Each $x_i \in S$ belongs to user $u_i$ who needs to obfuscate his secret using the notion of $d-$privacy defined in the ...
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### Proving the security of the public key BGV scheme

The security proof basically comes down to the following based on this paper. We want to show that two distributions are statistically indistinguishable. Say we have that $a,a′,x,x′$ are drawn from an ...
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1 vote
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### If the distinguishing advantage of A wrt distribution D_n, E_n is 1/poly(n) with probability .1, then are they not computationally indistinguishable?

As in the title, but to make more clear: If, with probability 0.1, an algorithm A can distinguish between two ensembles D_n, E_n (indexed by sec. paramater n), then are D_n, E_n not computationally ...
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### Partition/Range wise privacy

Consider two data streams $a_1,\cdots, a_n \in [a_{min}, a_{max}]$ and $b_1,\cdots, b_n \in [b_{min}, b_{max}]$, Such that $[a_{min}, a_{max}]$ and $[b_{min}, b_{max}]$ do not overlap. A Differential ...
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### Is there a public-key, "deal-less", all-or-nothing, "secret-length message" cryptosystem or some easy way to derive it?

I want to make an ecryption algorithm that is secure in, well, really many ways, which is hard I see, so I came up with some ideas of how to implement it using some primitives that I know and I ...
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### Secuirty definion of a ad hoc multi-input functional encryption scheme

I have to write an essay on the paper ad hoc multi-input functional encryption, and can't understand the security definition. In a nutshell it is a primitive that allow sources to supply encrypted ...
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### How Can Indistinguishability be Proven?

I'm curious on how computational indistinguishably is proved. For instance, would the following be computational indistinguishable? If it is, how do we prove it? Let $P_a$ be a probabilistic machine ...
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In each of those experiments, we have a function $Gen(x)$ who generates the key or a pair of keys respectively for symmetric or asymmetric algorithms. $x = 1^n$ : I read on other questions that is a \$...