Questions tagged [hash]

A cryptographic hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm makes it difficult to find two inputs with the same output or reconstruct the input from the output.

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Explaining the reason of radically more accuracy while using different set of hash functions instead of same set of hash functions on some operations

So I am looking for an explanation of an experiment. In this experiment, I took a set of k hash functions. Say the total number of data points I am working on is d. Call an algorithm A which used that ...
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Why HAIFA and sponge constructions are not prone to length extension attacks?

I was writing in a document about the flaws of the MD construction which pushed cryptographers to create different and more robust constructions. However, I don't know why HAIFA and Sponge ...
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Looking for specialists/software for cryptoanalysis of a hash function [closed]

I've created a hash function, conceptually similar to keccak (pseudo-random number generator derived from message). So far my function passes all tests of SMHasher ...
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Why does SHA2-224 use different IV's than SHA2-256?

Given that it's otherwise just a truncation, I can guess that being able to compute the 224 value from the 256 value is an unwanted property, but that's just speculation.
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Understanding birthday attacks on 256 bit hashing and 512 bit hashing [duplicate]

Does it make a difference against birthday attacks if the algorithm that I am using is 512 bit hashing?
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64 views

Does it make sense that a hash is separated by hyphens [closed]

I'm trying to solve a challenge that is no longer active. I failed it when it was active, and I still can't resolve it. The challenge showed me a hash, and I have no idea what kind it is, and how does ...
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Understanding the HAIFA (hash iterative framework) structure

Unfortunately, this structure doesn't even have a full Wikipedia on it. I'm struggling to understand it. There are no Youtube videos, Lectures, or any educational video on it. I want to understand how ...
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Is it safe to XOR-combine hashes by rotating them first?

I have a small number of hashes. I would like to combine them into a single hash. XORing the hashes ignores their order, which is important. Also, it could lead to a result of zero if there were an ...
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What is the sponge construction in simple terms?

I suggested to my client to use SHA3 instead of SHA2. I know that SHA3 is based on Keccak algorithm which won the NIST's competition. I want to explain the structure of sponge functions in very simple ...
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Why blake2b is the fastest despite it being 512 bits hashing algorithm?

I am struggling to understand why blake2b is faster than blake2s, despite that blake2b is 512 bits hashing. I hope someone can clarify that for me. I read the official paper for blake2b, but I am not ...
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Can an observer deduce a pre-shared key used multiple times on (nearly) random messages?

Imagine you took a standard one-way hashing algorithm (like SHA-256), and you implement it in hardware using simple logic gates. Now, replace each logic gate with an equivalent reversible logic gate (...
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How to get an output of SHA-1 with first 2-bit are zeros?

Can someone explain what are the ways to get an output of SHA-1 with first 2-bits which are zeros?
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Good key update algorithms for key evolving schemes

In schemes like SAKE(Symmetric-key Authenticated Key Exchange) , the master keys (used to authenticate parties and generate session keys) are evolving, ie undergo transition $K=update(K)$. What is a ...
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Is Blake2b vulnerable to length extension attacks?

There are very few resources for Blake2b apart from the official documentation and website. I would like to know if Blake2b is not vulnerable to length extension attacks unlike SHA2. I would like your ...
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Is 512 bits a more secure hashing than 256 bits?

I know that 512 bit hashing is more secure, but I don't really know why. I hope someone can help me to better understand it in more detail.
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Unique/Fast Hash for fixed size strings

I have a need to generate a unique hash for millions of Strings of same length. Would prefer a non cryptographic hashing algorithms for performance reasons. The hash can be of length upto 24 bytes, ...
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Where do hash functions get their preimage resistance?

I read through this answer and it seemed to make sense to me, but when I try to make a simpler answer to explain it to myself I lose something in the process. Here is the much simpler hash function I ...
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two-to-one hash in libsnark, what is it “exactly”?

I'm reviewing this test which prepares a zero knowledge proof of the preimage of an hash: https://github.com/mariogemoll/libsnark-tutorial/blob/sha256/src/test-knowledge-of-preimage.cpp In my (wrong) ...
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The length extension attack and security on length shortening of a hashed message by one byte

MD5, SHA1, SHA2 are vulnerable to length extension attacks Wikipedia:Length extension attack. Could is also be possible to generate $H(\text{message}[1..n-1])$ from $H(\text{message}[1..n])$ if I know ...
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45 views

HMAC for hash list

If I have a very large input to hash with a hash function vulnerable to length extention and I am using a hash list, should I HMAC each part of the input or just HMAC the final hash of all the hashes ?...
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Client-Side Encryption for a small app

I'm designing a small personal journal web application for my wife. I'm a crypto newb, but I want her to feel secure knowing only she will have access to her journal entries. I am thinking of the ...
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Can I use RSA as hash function?

My end goal is to have an encryption function $e$ and a hash function $H$ such that for all m we have: $$H(e(m)) = e(H(m))$$ This would work if we use RSA encryption along with RSA "hash", ...
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Creating hash data signatures using RSA-CRT

I have taken two prime numbers p=137 q=131 M=64 and i want to create a digital signature ...
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How SPHINCS+ Hash Signature ADRS structure define

can anyone help me to elaborate the structure of ADRS with example ( tree ADRS, layer ADRS, keypair ADRS etc)used to generate root SPHINCS+ signature. Also can some one help me to describe tree hash ...
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Does selectively generating keypairs with particular public-key hash prefix weaken the security?

I'd like to embed 8-bits of information by selecting only keypairs where a hash of the public key begins with those 8-bits. (The expected number of keypairs that will need to be generated is 256, so ...
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Subset Sum Hashes

This link discusses something called a 'subset-sum hash function'. I'm having a little difficulty understanding the algorithm, and I can't seem to find any existing implementations to reference. Could ...
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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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How can a collision attack using MD5 be used to break WOTS

It is stated in Winternitz One time signature security that MD5 is not safe for Winternitz due to collision attack. Given that WOTS generates multiple, say 32 private keys then hashing them a number ...
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How do herding attacks on hash functions work?

I read this paper Herding Hash Functions and the Nostradamus Attack, 2005 of Kelsey and Kohno on herding attacks but I do not understand how it works. Would anyone be able to give me a summary of how ...
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Modulo hashing scheme

Let's consider hashing of odd 256-bit number $L$ with 256-bit odd key $K$: $z = (2^{256}-L) \cdot K \bmod 2^{256}$ $z$ is the hashed number. If $K$ is selected randomly is it secure to hashing ...
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How does second pre-image attack on Merkle Signature Scheme work?

I understand that a second pre-image attack on the Merkle tree works by creating another Merkle tree using the intermediate nodes as the leaf nodes, and this will lead to the same root hash (public ...
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Design flaws when designing a MAC-function

Suppose we want to build a very basic hash function like this: $$c_i = h(c_{i-1},x_i) = c_{i-1}\oplus x_i \quad\quad mit \;\; i\geq1, c_0 = \operatorname{IV}$$ Now suppose we'd use this hash-function ...
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Manually creating a GPG Public Key

I want to manually create a GPG public key that can be imported into GPG, i.e. I want to create a file with a Public-Key Packet, a User ID Packet and a Signature Packet (for an example see here). I ...
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Small (code-size) hash functions

I am trying to implement a small encryption tool in as little code as possible as a learning exercise, and currently have managed to get everything to depend only on a HMAC construct. However, most ...
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Generating a XOR Hash function for a given group of numbers to maximise collisions

Given $x$, a vector of $m$ distinct bit vectors of bit length $N$, I want to use an XOR-hash $h$ such that all $x_i$ collide to the same value. I define an XOR hash $h$ which takes bit vector $q$ as ...
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Is there a way to prove knowledge of a limited resource like a phone number just to the people who already know about it?

For instance, let's say Bob's phone number is X and Alice has somehow identified that Bob's phone number is X. Now she doesn't have a direct way to contact Bob, so she wants to post in a public forum ...
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Hash into elliptic curves for private set intersection

Would it be insecure to hash a message $m$ to an elliptic curve point by multiplying it to some generator $G$ for the purpose of a private set intersection ? $$ M = hash(m) * G $$ I keep seeing ...
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Is $f_N$ in this hash function is Matyas-Meyer-Oseas scheme?

I propose a hash function as following: H is an Merkle-Damgard hash function with a compression function $f: \{0,1\}^{3n} \to \{0, 1\}^{2n}$. Output function $f_N: \{0,1\}^{3n} \to \{0, 1\}^n$. M is ...
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Is it easy to crack a hashed phone number?

I want to SHA256 hash phone numbers in order to hide them. Is this a good idea? Are there any other ways I could make this safe?
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Security implication of concatenating two hashes using different algorithms

Background Hashing files is an expensive thing for CPU. I am tasked to write a secure digital signature scheme. For that, I decided to check the integrity of files using Hash/Digest. To be more secure,...
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Is storing salts encrypted a good idea?

I've read that storing password hashes in a database, you can store the salt in plaintext alongside the actual hash with no detriment to security. I was thinking that one could derive a key from the ...
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Padding of SHA-3

SHA-3 uses Padding, so the original message has a certain length. In the case of SHA-3-512 each block has the size of 576, so any message must be padded, such that it is a multiple of the blocksize ...
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Looking for a Non-textual hashing function

Pardon my terminology, but is there a hashing function of some sort which accepts a string as input and generates a non-textual output of some sort, or perhaps a unique output that can be used to draw ...
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Is using Fiat-shamir Heuristic safe?

What I'd like to do is to have the Prover store a value x where x remains hidden. From x, I'...
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1answer
64 views

Combining algorithms for password storage?

Is it more secure to combine algorithms for password hashing, for example, Scrypt, Bcrypt, SHA-3, etc.? If an attacker wants to use dedicated hardware, he would need one for each algorithm. However, I ...
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Does there exist a hash function which has a fixed point? [duplicate]

Does there exist a hash function $h$ and an input $x$ such that $h(x) = x$? I believe this is a special case of collision-resistance. I imagine such a case is guaranteed not to be possible (otherwise ...
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Why AEAD instead of encrypting with a simple hash?

I hear a lot about AEAD encryption (GCM, EAX, ...). Why is it unsecure (it seems to be as AEAD exists) to do do that: Imagine a block of data, hash it, append the hash to the data, then encrypt the ...
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Using SHA2 as random number generator?

I need to generate secure pseudorandom numbers in an embedded system. Instead of having to port some RNG library, could I just use an existing SHA2 function as a random number generator (n-th random ...
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Why cant we use AES to hash a password, instead of a hash function?

AES needs a key in order to work, hashing-algorithms do not. Suppose we have a fixed key for AES, why don't we simply hash our keys with that? As with hash functions, AES has arbitrary input size, ...
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Would increasing the “target space” of MD5 collisions make it significantly easier to find a collision?

This is tangential to this question, which asks about generating a file to match an exact MD5 hash. My question is if it would be significantly easier to generate a file that is "within X digits ...

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