All Questions
Tagged with cryptography hash-function
33
questions
1
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2
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154
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How can I do Gaussian elimination of a $32 \times 32$ bit matrix?
I have been looking at how to reverse the sigma operation in the sha256 hash and in several places I have seen that you have to make a $32 \times 32$ bit matrix and then solve it with Gaussian ...
- 13
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1
answer
171
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What is the purpose of the "diffusion" property of a hash function? [closed]
https://www.cs.cornell.edu/courses/cs312/2008sp/lectures/lec21.html says
For a hash table to work well, we want the hash function to have two
properties:
Injection: for two keys k1 ≠ k2, the hash ...
- 47.7k
0
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0
answers
126
views
Is it possible to construct a hash function that accepts multiple keys and returns the same value if at least one key is the same?
How to construct a hash function that accepts multiple keys as input and returns the same value if at least one input key is the same, no matter which keys are identical?
For example, the desired hash ...
- 83
0
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0
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181
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Time Complexity Baby Steps Giant Steps
This has been driving me mad. On wikipedia's page on baby steps giant steps it gives the time complexity of the algorithm as $O(\sqrt n)$. It even gives looking up a value in a hash table as how you ...
0
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1
answer
85
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What system has modular inverses for non primes too?
Is there a system that has modular inverses for non prime mods?
Ultimately what I am trying to do is design a hash function that given a list of n outputs (mod m) and inputs (large arbitrary integers),...
- 101
1
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1
answer
139
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Domain of hash function
I am reading Buchmann's Introduction to Cryptography, 2nd ed.
On page 267,
$G$ is a finite cyclic group of prime order $q$. $a\in\mathbb{Z}_{q}=\mathbb{Z}/q\mathbb{Z}$. $h:\{0,1\}^{*}\to G$ is a hash ...
- 1,889
3
votes
1
answer
83
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Why is $a^{-1} \cdot a \equiv 1 \text{ mod } m$ a lemma in universal hashing? [duplicate]
I have been given the following lemma in a online lecture on universal hashing:
Lemma: Let m be a prime. For any $a \in \{ 1, \dots, m-1 \} $ there exists a unique inverse $a^{-1}$ such that
$a^{-1} \...
- 301
1
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0
answers
14
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Is there a hash-like function from pointed digraphs where if A and B differ only in the placement of the point, this is clear in the hash?
I want a cryptographically secure hash-like function (it need not output integers, it could be any data type) which takes directed graphs with a single marked point as input, so that if graphs A and B ...
1
vote
1
answer
58
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Understanding hash functions.
What I understand by a Hash function, is a function $H$, such that taking an input $x$ of some bit-length $L$, produces an output $y$ of some bit-length $l$ such that $L >> l$ (where ">>" means ...
- 449
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0
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70
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A random oracle as a CRHF
Reading through the book Introduction to Modern Cryptography by Katz/Lindell, I'm having some trouble understanding this part.
(It's on p.178 in 2e, chapter 5.5)
What I'm struggling with are:
How ...
- 23
1
vote
1
answer
38
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How difficult would it be to find valid answers for this hash arrangement?
If $A$ is a 160-bit number, and $X \& Y$ are two SHA-1 hashes, to be generated such that the 320-bit number $X\mathbin\|A$ hashed to $Y$, and the 320-bit number $A \mathbin\| Y$ hashed to $X$?
...
- 11
2
votes
3
answers
62
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How can I increase the complexity of a number and maintain uniqueness
I have an 8-digit number and you have an 8-digit number - I want to see if our numbers are the same without either of us passing the other our actual number. Hashing the numbers is the obvious ...
0
votes
1
answer
151
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Distinguishing cryptographic properties: hiding and collision resistance
I saw from Another question the following definitions, which clarifies somewhat:
Collision-resistance:
Given: $x$ and $h(x)$
Hard to find: $y$ that is distinct from $x$ and such that $h(y)=h(x)$.
...
1
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1
answer
74
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Given a boolen hash function (based on XOR), find the $n^{th}$ key for a specific hash.
A boolen hash function is given that takes a hexadecimal key as input and returns the hash for that key (hash can be only 0 or 1). The hash function is based on XORing bits of the key.
For example, ...
- 181
1
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2
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1k
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Why do we pick ax + b when doing universal hashing?
Why can't we pick just $x + b$ for example? I know that for universal hashing the Pr[$h(x) == h(y)$] $\leq 1/|n|$
But with the same hash function, just without the $a$ we can get $h(k) = (($k$ + b$ ...
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