a situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.
See also the hash wiki tag.
Questions tagged [hash-collision]
233 questions
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Does halving every SHA224 2 bytes to 1 byte to halve the hash length introduce a higher collision risk?
Let's say I have strings that need not be reversible and let's say I use SHA224 to hash it.
The hash of hello world is 2f05477fc24bb4faefd86517156dafdecec45b8ad3cf2522a563582b and its length is 56 bytes.
What if I convert every two chars to its…
Alper Turan
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Hash Table: Should I increase the element count on collisions?
Right now my hash tables count the number of every element inserted into the hash table. I use this count, with the total hash table size, to calculate the load factor and when it reaches like 70%, I rehash it.
I was thinking that maybe I should…
rfgamaral
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2 answers
Separate chaining for HashTables in Java
Based on the following code snippet :
Hashtable balance = new Hashtable();
Enumeration names;
String str;
double bal;
balance.put("Zara", new Double(3434.34)); //first entry for Zara
balance.put("Mahnaz", new Double(123.22));
…
Dubby
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Why is my identifier collision rate increasing?
I'm using a hash of IP + User Agent as a unique identifier for every user that visits a website. This is a simple scheme with a pretty clear pitfall: identifier collisions. Multiple individuals browse the internet with the same IP + user agent…
samthebrand
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2 answers
Java : How to make this hash table function work on a much larger scale
I have the following code, that will take 30 strings (that are numbers) and put them into a hash table after computing them with "%29"
import java.util.Arrays;
public class HashFunction {
String[] theArray;
int arraySize;
int…
user3274463
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which hash functions are orthogonal to each other?
I'm interested in multi-level data integrity checking and correcting. Where multiple error correcting codes are being used (they can be 2 of the same type of codes). I'm under the impression that a system using 2 codes would achieve maximum…
BeowulfNode42
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Is using unique data better than random data for a hash?
I need to generate global unique ids by hashing some data.
On the one hand, I could use a combination of timestamp and network address, which is unique since every computer can only create one id at the same time. But since this data is to long I'd…
danijar
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How is data retrieved from a HashTable in collision?
According to this, time complexity of search in a hashtable is O(1).
However if there is a collision, then obviously this should be O(1) + something.
My question is:
When you say
get(someKey)
from a hashtable, the hashing function is applied to…
Koray Tugay
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Collision rates for trimmed SHA1- hashes
With my webapp I'm storing cached files with a hash generated filename in various subdirectories to optimize performance levels. One way I know that I could improve performance also would be to ensure that the generated names follow a 8.3 filename…
James South
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Probing hash tables
I am implementing a hash table for a project, using 3 different kinds of probing. Right now I'm working on linear.
For linear probing, I understand how the probing works, and my instructor implied he wanted the step size to be 1. The thing is, no…
Desmond Lee
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11 answers
Chaining in HashMap
Code:
public static void main(String[] args) {
Map map= new HashMap();
map.put("a", "s");
map.put("a", "v");
System.out.println(map.get("a"));
}
Now, as per my understanding, since the key values in…
Kraken
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2 answers
Hash collision worries
If I have a system where a hash is generated out of a total permutation of 1 million possibilities. If there's a 10% chance of a collision, should I worry about the generating algorithm running 5 times?
I have a system similar to jsfiddle, where a…
qwertymk
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2 answers
What hash function is better?
I write my implementation of HashMap in Java. I use open addressing for collision resolution. For better key distribution I want use a nice hash function for int hashcode of key. I dont know what hash function is better for it?
public int getIndex(K…
gizzy
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3 answers
Hash Cryptographic Function Output Anomolies
Anyone know if MD5, Whirlpool, SHA[n], etc., have any "special" input that might get a hexdigest output to align into:
All numeric characters
All alpha characters
All of the same character/pattern repeated consistently or entirely
Example in…
yurisich
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3 answers
How can i count the collisions in this hash function?
This is a prefix hashing function. i want to count the number of collisions in this method but i am not sure how to do it. It seems like it might be simple but i just cant think of a great way to do it....
int HashTable_qp::preHash(string & key, int…
user977154
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