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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Generate a key with a size bigger than the hash output length/security, is it possible? [duplicate]
Let's suppose I want to generate a 2048-bit key from a hash function with security up to 512-bits (such as Blake2b).
I take 4 high-resolution photos, hash them with a hash output length of 512-bits ...
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Hashing Passwords and Hash Functions
I'm a complete noob. I was reading up on hash functions. So if a bank has its user password's run through a hash function, it'll produce a unique hash for every password right? Thus, even if hackers ...
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Checking if a function is collision-resistant
Consider a prime order cyclic group $\Bbb G$ of order $q$ with generator $g$. Then consider the function$$f:\Bbb Z^n_q\to\Bbb G\\(\alpha_1,\alpha_2,...,\alpha_n)\mapsto g^{\alpha_1\cdot\alpha_2...\...
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Looking for a hash function (not necessarily cryptographic) where similar inputs return dissimilar outputs
I have the need to take a string and return a color. One requirement is that the same name always returns the same color. Another is that similar names should not return similar colors.
I understand ...
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More efficient way of iterative hashing
Here is a possible way to perform iterative cryptographic hashing twice as fast as in the ordinary way.
Given a compression function $f: \{0,1\}^{a+b} \rightarrow \{0,1\}^b$. Assume the message is of ...
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Is this authentication protocol secure against both eavesdropping and server database disclosure?
Consider the following protocol from the book "Network Security: Private Communication in a Public World" by Kaufman et al.
Alice knows a password. Bob, a server that will authenticate ...
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vary length hash collision on deterministic block cipher
I am trying to learn attack on hash collision. I guess for this scheme, it might be possible to use messages with different lengths to find a pair of same ciphertexts. An attempt is to use the same ...
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How Davies–Meyer does work? [duplicate]
I am here so if I asked something wrong or in the wrong way please let me know.
How to hash compression large data into the fixed size of the string.
Edit:
How Davies–Meyer does work?
Take the example ...
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Cryptographic hash function to map interval onto itself
Is there any existing approach to construct perfect hash function that map [0, M) to [0, M)? It should be one to one mapping and ...
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How to find strength of a cryptographic hash function?
I am having an idea to create a cryptographic hashing algorithm. I found a mathematical function $f: x \rightarrow y$ . By using Merkle-Damgård construction wide pipe, I designed a hashing function. ...
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Using the hash of the plaintext as the key
I want to start off by being very clear: I'm not designing a system around this, this is 100% a hypothetical I was toying with.
Is there any harm in using the cryptographic hash of a plaintext as the ...
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Generalizing randomized permutation functions
The paper on the "SNEIKEN and SNEIKHA" AE and HASH sponge-based algorithms, respectively, presents a 512-bit permutation function "SNEIK512" that, unlike other permutations (ie: ...
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Is a perfect hash function the same concept as a collision-resistant hash function?
About collision-resistant hash functions, in Katz's Introduction to Modern Cryptography,
6.1 Definitions
Hash functions are simply functions that take inputs of some length and
compress them into ...
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How to assign md5 of another file to one wav file? [duplicate]
Good afternoon . Please tell me how to change the md5 hash of one wav file to the md5 hash of another wav file. I want to bypass the anti-cheat check on md5. Maybe there are online paid services? I ...
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Are pseudorandom generators, pseudorandom permutations and hash functions all keyless?
In Katz's Introduction to Modern Cryptography,
Chapter 7 Practical Constructions of Symmetric-Key Primitives
In previous chapters we have demonstrated how secure encryption
schemes and message ...
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Why is RSA not a hashfunction?
The RSA-Assumption says that $(GenSP,F,SampleX)$ is one-way. So if we initialize an instance of RSA $(n,e), (n,d)$ and fairly forget the secret-key and SampleX uniformly distributed over $X, F = x^e \...
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Can you recover $y$ if you have $x$ in Pedersen hash?
(this might be a silly question)
Pedersen hash works in the following way: $(x, y) = kG$ where $k$ is the pre-image and $(x, y)$ is the resulting hash.
Say we hide part of the hash to preserve privacy....
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Checksum function verifying even numbers as the sum of two halves
Does the following checksum function make sense?
I am attempting to show that for all even numbers there exists at least two summands that, when normalized to $\frac{1}{2}$, asymptotically sum to 1:
$\...
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SHA-256 compression functions without padding
Looking at the example of the null input (512 bits), it takes as input:
input (Hex):
...
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Why do we need both bitmasks and keyed hash in SPHINCS+
I think one of them is related to multitarget attacks and the other is related to collision attacks. But I cannot find how hash based crypto related to hash collisions.
1-) Consider the following ...
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Inverses of the operation $(a,b) \mapsto a \oplus b\oplus ((a \land b) \ll 1)$ for fixed bit length
Background. In their paper about the cryptographic scheme NORX, the authors use a fast approximation of + by bitwise operations (taking fewer CPU cycles than proper addition) using the formula $$a+b \;...
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Do proof of work hash function arguments have anything in common?
Some proof of work hashes have a lot of initial zeros. Do the arguments to the hash functions giving these zero containing hashes have anything in common, or are they stochastic?
What I am looking ...
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Understanding intermediate values - SHA2 - 512
I am trying to understand SHA2 - 512 algorithm, so I am following this document which has the intermediate values for the string "abc". At t=0, the values ...
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Can a collision resistant hash return zero?
Recently, I have been reading the original proof of GCM.
It mentioned the properties of "almost universal" and "return zero" for hash function.
I wonder if there is a connection ...
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Will Hashing Multiple Times Be More, Less, Or Similarly Secure As Hashing Once
Will Hashing Multiple Times Be More, Less, Or Similarly Secure As Hashing Once?
Flushing out this question:
I saw this claim:
List item: ...
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Understanding Hash collisions - why bad?
I read few answers about the question: why are hash collisions so dangerous?
But did not get a really satisfying answer.
Assume we are the first people who found a SHA256-collision, like
sha256($§&...
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Can I treat SHA-256 hashes as 64 fair dice rolls with numbers between 1 and 16?
My understanding was that SHA-256 is pretty random or "random" enough.
I assumed that would mean that every character would behave like a 1 to 16 dice roll.
With this assumption, I would ...
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Collision resistance analysis
I am learning about collision resistance security notion of hash functions. However, I got confused when collision resistance experiment started using "keyed" hash functions in the ...
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Can you use a keyed hash function as a general purpose hash function?
I'm working with SWIFFT, a provably secure keyed hash function, which is desirable to me. Unfortunately from what I gather it is ONLY a keyed hash function. Would there be any disadvantages or ...
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Which hashing function is good enough for session IDs?
Background
I'm building a URL shortener, and the URL to shorten may contain a SessionId.
For the URL shortener to not compromise the security of the SessionId, I must use a shortening strategy that ...
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Finding collisions of polynomial rolling hashes
A polynomial hash defines a hash as $H = c_1a^{k-1} + c_2a^{k-2} ... + c_ka^0$, all modulo $2^n$ (that is, in $GF(2^n)$).
For brevity, let $c$ be a $k$ dimensional vector (encapsulating all the ...
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Hash Comparison to Detect Ransomware File Encryption
As detailed in a separate question, I thought I had a way to detect the type of ransomware that encrypts files silently, and then decrypts them on the fly, so as to prevent the user from realizing ...
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How safe is my pseudonymization procedure?
I work for an institution where patient data is collected and I am supposed to encrypt it. At the moment I do the following steps (with R):
Randomly assigning an ...
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Are such verification wormholes known, or even possible?
1. Scenario
Suppose that we have a source that is generating one random value per, say, minute. So we have random value $x_1$ in $1$st minute, $x_2$ in $2$nd minute, $\ldots$, $x_n$ in the $n$th ...
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Impersonation attack on Lamport's one time password
So here I am, googling my brain on the possibilities of impersonation attempts by a MITM attacker on Lamport's one-time password scheme.
Here's my scenario:
Say we have a client and server setup. ...
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I don't quite understand hashing
I don't quite understand hashing, for encryption or otherwise.
So, if you have a website, and a user signs up, you store his password as a hash.
When they log in, your website takes the submitted ...
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Standard way to generate pseudorandom bytes on demand
I considered Extendable-Output Function (XOF) with a random seed but it seems I would have to specify the output length at the start and store the entire output. I don't know how many bytes I will ...
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Does concept "Collision Resistance" and "Binding Commitment" in cryptography similar?
I found there are two perplexing and related concept "Collision Resistance" and "Computation Binding in Commitment" in cryptography.
I found the wikipedia's explanation is ...
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How to map output of SHA to $\mathbb{F}_q^n$
I have an arbitrary string. I want to know how to implement a hash function $H: \{0,1\}^* \to \mathbb F_q^n$ which takes arbitrary strings to an element of $\mathbb{F}_q^n$. Here $\mathbb{F}_q$ ...
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Argon2 allows a huge key length in input, but does it really provide the security of the key provided?
I read the Argon2 specification.
It says in 3.1 (Page #5):
Secret value K (serves as key if necessary, but we do not assume any key use by default) may have any length from $0$ to $2^{32}\text{-}1$ ...
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How to most inexpensively extract 1 byte of uniformly distributed entropy from a 32-byte Curve25519 EC point
I'm looking for the simplest and most inexpensive hash with the following properties:
Input: A 32-byte Curve25519 EC point containing approximately 125 bits of non-uniformly distributed entropy (...
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Hash paradox in an image file that contain hash text?
Is it possible to include a hash digest visibly in an image, such that the hash of the image itself is that same digest?
When we draw the text of the hash in the image, we will of course change the ...
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Checking equivalence among distributed sets
I have elements from $\{0, 1\}^{n}$ (range of a hash function)
The master $A$ can have any subset of this range.
There are clients that each have a subset from the space, too.
I want to make sure that ...
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Is there collision in encryption like in hash functions?
In hash functions, $h(m) = h(m_1)$ is called collision and is very undesired that they are feasible to find as it undermines hash security. However, is there essentially analogous concern in ...
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Benefits of hashing a particular seed in a PRNG
This question is linked with this question (stackoverflow) where I asked about a specific implementation detail of Python's random number generator (Mersenne Twister). Here, I have a slightly ...
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Can a service provide a hash/encryption key to others that it itself cannot use?
Consider a service $S$ that receives hashes of documents from a number of providers. If two hashes match, it notifies the providers. We do not want anyone at the service to be able to identify the ...
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Can two different hash function create two unlinkable `ed25519` keys from the same randomness?
Assume the following scenario:
Alice has access to 32 bytes of true randomness $s$.
Alice hashes $s$ with SHA-512, and uses the resulting hash as the secret $d_{A}$ for ...
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Hash verification by key
I want to implement the following algorithm, but don't know what tools to use.
D - data
I generate some universal value for D - Y
I generate some random key - K, get a hash of D by this key - H
I ...
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What does j9T mean in yescrypt (from /etc/shadow)? [closed]
For example I have a shadow string
$y$j9T$PaFEMV0mbpeadmHDv0Lp31$G/LliR3MqgdjEBcFC1E.s/3vlRofsZ0Wn5JyZHXAol5
There are 4 parts
id : y (yescrypt)
param : j9T
salt :...
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Encryption with AES128 (ECB) and Key validation
In my new challenge-project my server once upon a time is broadcasting an "onion" made of three layers encrypted with AES128 (ECB) - 16 bytes long over WiFi.
I am using a WiFi Beacon Frame, ...
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