# Questions tagged [universal-hash]

In mathematics and computing, universal hashing (in a randomized algorithm or data structure) refers to selecting a hash function at random from a family of hash functions with a certain mathematical property.

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### What does the leftover hash lemma guarantee for a specific hash function?

Suppose I sample a matrix $h$ from $\mathbb{Z}_2^{l \times n}$ where each entry in $h$ is $1$ with probability 1/2. Suppose I also have a set $S\subset \{0,1\}^n$, and I define a random variable $X$ ...
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### What is the advantage of using hash function families instead of a single hash function?

My guess would be that families are more secure. In which way though? I have seen claims that hash function families can be collision resistant while single hash functions can not be. Is this true? ...
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### Is a PRF pairwise independently and uniformly distributed

The notation of a strongly universal function was introduced by Wegman and Carter here and it states, that such a function has to be pairwise independently and uniformly distributed. I would like to ...
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### Do "superfast" keyed hash functions exist?

A common family of requirements for (cryptographic) keyed hash functions is that the function $h(k,-)$ should have good collision resistance for all keys $k$, even if the key $k$ is known to the ...
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### The rigorous proof in the commitment based on CRHF

I'm reading about the lecture of Yevgeniy Dodis. In his lecture 14, section 2.3.2, gives a commitment construction based on CRHF, but the proof of hiding is high-level. I want to know the rigorous ...
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### UOWHF vs CRHF / Relevance of UOWHF

What's the difference between UOWHF and CRHF and why are UOWHF useful? As far as I understand, Universal One-Way Hash Functions are an alternative to CRHF. While for CRHF it is hard, given randomly ...
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### Create a control hash string from different sources, is there a difference, advantage or disadvantage in comparison when using this ways?

I wanna create from several inputs/sources should be formed into one hash value for controlling of different thinks later. Example: String + File String + String File + File String + File + String ...
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### What are the differences between a UHF (as used in cryptography) and a cryptographic hash function?

After reading about UHFs from different sources (From Algorithm books to Crypto books), I am still thoroughly confused about them. How is a UHF different from other cryptographically secure hashing ...
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### Why does the hashfamily of all functions with $\{h \in H_0 | h:U \rightarrow V\}$ satisfy universal hashing?

I read in our university lecture on hashing that it would be good (even though it is way to space intensive) if we could take the set of all function from $U \rightarrow V$ to satisfy the following ...
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### How does the probabilty for universal hashing work out?

Hey for universal hashing we say the following: Definition: A randomized algorithm $H$ for constructing hash functions $h\colon U \to \{1,\ldots,M\}$ is universal if for all $x \neq y$ in $U$, we have ...
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### How to look for implementations of universal hashing?

Being a physicist, I know very little about cryptography. In fact, the main two practical aspects I've learned so far are: Unless you're an expert, 1. Don't try to invent new cryptosystems and 2. Don'...
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### Low weight linear $\varepsilon$-universal hash function

According to the definition, an $\varepsilon$-universal linear hash function family, given a field $\mathbb{F}$, is a set of linear transformations $\mathcal{H} \subseteq \mathbb{F}^{m,n}$ such that ...
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### Can universal hashing functions be (ab)used as stream ciphers?

These days, universal hashing functions like GHASH and Poly1305 are very trendy because of their simplicity and speed. Now during a discussion related to export restrictions, it came up that mainly ...
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