# Questions tagged [pseudo-random-function]

A pseudo-random function (PRF) is a family of deterministic functions indexed by a parameter, such that a randomly selected instance is computationally indistinguishable from a uniformly random function with the same input and output spaces.

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### Is this a secure PRF?

Let $F:\{0,1\}^n\times\{0,1\}^n\to\{0,1\}^n$ be a secure PRF. Consider a construction of a new PRF $F':\{0,1\}^n\times\{0,1\}^n\to\{0,1\}^n$ as follows $F'_{k}(x)=F_{F_{k}(x)}(x)$. Is $F'$ secure? ...
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### How to understand the counterexample constructed in the PRP/PRF switching lemma towards the standard proof?

I'm reading a paper Code-Based Game-Playing Proofs and the Security of Triple Encryption , which indicates an error on the standard proof of the PRP/PRF switching lemma using the conditional ...
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### Verifiable OPRF from general ZKP?

We know how to build a signature scheme from ZKP and hashing: For signing, the signer creates a ZK-PoK $Sig$ that it knows $k$ such that $\text{H}(k) = \text{id}$, and includes the message $m$ in the ...
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### How to proof that G is a PRG? [closed]

I followed a lesson this year about Introduction to Cryptography and Anonymous Communication and I am going to retake the exam of this lesson. I was doing exercises to practice but we don't have the ...
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### What is exactly Randstorm vulnerability?

I've read the article from Unciphered about it, multiple times, and still fail to understand it It basically says that wallets generated by BitcoinJs front end library from 2011 to 2015 are vulnerable ...
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### prove there exists a non-adaptive PRF that is not an (adaptive) PRF

A function family is a non-adaptive PRF, if it is a PRF s,but its security should only holds against non-adaptive distinguishers (non-adaptive distinguishers make all there queries at once)prf
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### PRF collision search for input smaller than output

Assume a given pseudo-random function $H:\{0,1\}^a\mapsto\{0,1\}^b$ with $b\in[104,256]$ and $b/2<a<b$. We want to exhibit a collision if there is one, which has probability $>63\%$. We are ...
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### Is it secure to do subfield vector oblivious linear evaluation (VOLE) over a Ring $\mathbb{Z}_{2^k}$?

In the paper "Efficient Pseudorandom Correlation Generators: Silent OT Extension and More (https://doi.org/10.1007/978-3-030-26954-8)" Boyle et. al. proposed subfield vole. For standard ...
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### Is there a way to make a pseudorandom function to generate decimal numbers in a specified range and not only producing big ones?

When I try to generate decimal numbers in the range 0-18446744073709551616 using a hash function I always get big numbers like this: ...
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### When the input size in a PRF is larger than the output and many inputs will generate the same output, but why AES-256 in CTR mode is considered safe?

I know that if the input size in a pseurandom-function is larger than its output, many different inputs will generate the same output by the Pigeonhole principle (I also read an article related to ...
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### Computing the advantage when checking PRF

I am reading a pdf on pseudorandom function I found here https://www.cs.utexas.edu/~dwu4/courses/sp21/static/reductions.pdf My problem/struggle is with the computation of the distinguisher's $B$ ...
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### Distribution distinguishability as a decision problem

In the definition of a pseudorandom function, we consider two distributions $D_0$ and $D_1$ over functions, where $D_0$ is the distribution of a random function and $D_1$ is the distribution of a ...
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