# Questions tagged [hash]

Mathematical function that maps arbitrarily-sized data to fixed-size integers, often used as keys in hash tables or to help ensure data integrity

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### How 'Avalanche Effect' got its name?

I wonder how or why Avalanche Effect got its name. Avalanche Effect is a desirable property of cryptographic algorithms, wherein if an input is changed slightly (...
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### Why mod operation can be used as hash function

I'm new here, and I'm currently trying to understand why mod operation can be used as a hash function. For example, consider the function $h(x)=x\mod 2^{256}$, where $x$ can be a string of any length. ...
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### Hash function to return only positive number from integer

What would be a good hash function that will return a positive integer value, even if the key is an negative integer value? How do I pick a hash function? So what I would want is to associate negative ...
117 views

### Choosing an independent hash function, given hash function value

Supposed we have a function $h:U\to [m_1]$. Given this hash function, can we generate without using randomization or a universal hash collection another hash $h':U \to [m_2]$, which depends on $h$ ...
244 views

### Most space-efficient lossy dictionary?

Short version: What is the most space-efficient lossy dictionary (with given false positive and false negative rates)? Long version: A lossy dictionary is a data structure $D$ that encodes a set $S$ ...
466 views

### How to get all in constant time?

We are planning to design a system where following operations are supported. ...
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### Pairwise hash functions that are independent from each other

Is there there a way to build a collection of universal hash functions $H=\{h| h:U\to D \}$ where the values of two hash functions are independent one from another? i.e., \$\Pr_{h_1,h_2\in H}(h_1(x)=y ...
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### Computing hash of a compound key

Why is the initial value of hash 17 and not 0? ...