# Questions tagged [one-way-function]

A function which is easy to compute but hard to invert (i.e. find preimages for). The existence of one-way functions implies the possibility of many useful cryptographic schemes. No one-way functions have so far been proven to exist, but many likely candidates exist.

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### If a permutation $f$ is not one way, what can we say about $f^{p(n)}$?

Consider a permutation $f:\{0,1\}^*\rightarrow \{0,1\}^*$, which is not a one-way function, i.e. there exists an efficient probabilistic adversary $\mathcal{A}$ and some polynomial $q(n)$ such that ...
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### Can a One way function also be its inverse?

This is from my homework: Prove that if there exists a one-way function, then there exists a one-way function f such that $f(0^n ) = 0^n$ for every $n$. Note that now for infinitely many values $y$...
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### Necessary conditions for construction of $n$ to $p(n)$ pseudorandom generators from $n$ to $n+1$ generators?

Given a polynomial time deterministic algorithm $G_1:\{0,1\}^n \rightarrow \{0,1\}^{n+1}$, consider the function $G:\{0,1\}^n \rightarrow \{0,1\}^{p(n)}$ constructed as follows: Let $s \in \{0,1\}^n$ ...
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### Existence of MAC implies existence of OWF

I'm having trouble understanding how the existence of a MAC implies the existence of an OWF. If the MAC protocol is $(\operatorname{Gen}, \operatorname{MAC}, \operatorname{Ver})$ such that for any ...
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### One-way Functions for Floating Points

Are there any commutative one-way functions for floating points? I tried to explain why I need these functions. First, I describe the problem on a high level and then I further formalize it; There ...
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### Subset-sum one way function is one way on it's iterates if subset-sum is one-way

Working through the Moni Naor's slides from his lecture Foundations of cryptography (Lecture 3), the slides state that the subset sum function is one-way on its iterates if it is one-way, where the ...
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### Can we construct a PRF directly from a one way permutation function?

In Introduction to Modern Cryptography first a pseudo random generator (PRG) is constructed from a one way function (OWF). After that the PRG is used to to construct pseudorandom functions (PRF). Is ...
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### Newbie question: one-way functions in cryptography

I'm reading this article on the basics of cryptography and it says that the main principle is about taking such an algorithm that knowing the end result and the algorithm, an eavesdropper wouldn't be ...
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### If trapdoor OWF exists then f is a trapdoor OWF, is there such a construction?

Is there a known construction of f, such that given that a trapdoor OWF exists then f is a trapdoor OWF, so we can construct inefficient cryptomania, ala Levin's construction for minicrypt in "The ...
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### Is $f(x) = g(x) ⊕ g(\bar{x})$ a one-way function where $g(x)$ is a OWF?

Let $g$ be a one-way function, and let $f(x) = g(x) ⊕ g(\bar{x})$ (where the bar over x denotes bitwise complement). Is $f$ necessarily a one-way function?
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### Clarification of one-way property of hash functions

One-way property: computationally infeasible to find data mapping to specific hash The definition above is a little vague, if we have h(x) = floor(log(x)), ...
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### Is a one-way function pseudorandom?

For one-way function $f$ I understand that $g(x)=0^{n}\mathbin\|f(x)$ is a one- way function with respect to $2n$, where there is $n$ bits of $0$ in the beginning and the output of $f$ in the second ...
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### Concept of hashing a group of data and validating if a value exists within the group

When learning about cryptography and hashing, I remember seeing a concept where you could hash a number of values (ID's for example) and then validate against the hash, not storing the original IDs. ...
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### Composition of weak one way function is not a strong one way function

Given $f(x)$, a weak one-way permutation, how to prove that $f^T(x)$ is not a strong one-way function? Here $f^T$ denotes $T$ times self composition of $f$ and $T$ is a polynomial in input length.
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### Why the output length of a KDF should be the same as the underlying OWF?

Quote: The chosen output length of the key derivation function SHOULD be the same as the length of the underlying one-way function output. Could someone please help explain the benefits and ...
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### What does approved one-way function mean?

In one of their documents, NIST recommends using an approved one-way function, followed by a list of such functions, such as HMAC, KMAC, etc.. However, the wikipedia page says: Unsolved problem in ...
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### What is the one way function in ECC?

In the RSA algorithm it's the the integer factorisation problem, it's easy to multiply the two large primes to generate n, but given just n it's very difficult to find the constitutent primes. In the ...