# Questions tagged [collision-resistance]

Difficulty of finding two different inputs that hash to the same value

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### Determine if a Hash function is pre-image resistant and collision free

I'm so confused by this kind of exercise. We have that $n = p * q$, where $p$ and $q$ are prime numbers. Let's examine this hash function: $h(x) = x^2 \mod n$. Determine if the hash function is pre-...
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### Can we combine two AES (with block size 128) to to a block cipher with a block size 192 which is collision-resistant?

Encrypting values with AES we only need about $2^{64}$ trials until we finding an already used value (some collision). This can be done these days with easy. To make this harder can we combine two AES ...
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### Proof of computationally binding correct?

I have defined the following commitment scheme and would like to prove that it is statistically hiding and computationally binding, but I'm not sure if my proof is accurate: For $h$, a collision ...
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### Do L-trees remove the need of collision resistance hashes in XMSS MT?

I read that the bitmasks in XMSS-MT lower the security requirements from a collision resistant undetectable hash to a 2nd preimage resistant undetectable hash (see LMS vs XMSS: Comparion of two Hash-...
1 vote
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### What is an advantage of the Charles--Lauter--Goren hash function?

What is an advantage of the Charles--Lauter--Goren hash function (based on isogenies of elliptic curves) among other provably secure collision-resistance hash functions ? I heard that it is slower.
1 vote
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### Hash of concatenated values (one public, one private)

Assume two end-points $A, B$. $A$ sends to $B$ a $Hash(pv||key)$, where $pv$ is a public value that can be intercepted by attackers. The $key$ is a common secure shared key in both end-points, and $||$...
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### Randomness and authentication on short value outputs (48 bits)

I want to implement a client that generates random 48-bit values and send them as broadcast messages. We assume also there is a legitimate receiver getting those values (so, there is some sort of pre-...
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### non-reversible additive cryptographic hash algorithm

I need a lightweight cryptographic hash function which is additive but not reversible, however I'm not sure such a function exists! (it would be better if it works in multisets as well) By additive I ...
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### Why we need DSPR or Eq. 14 for the proof of SPHNICS+?

The paper says that We show that preimage resistance (PRE) follows tightly from the conjunction of second-preimage resistance (SPR) and decisional second-preimage resistance (DSPR). As I understand ...
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1 vote
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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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1 vote
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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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### 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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### can you generate an ID number quickly, with no collisions, and without IDs revealing information?

Is there a standard way to generate ID numbers one after the other such that: You can guarantee, or almost guarantee, that you avoid collisions. (By "almost guarantee", I mean for example ...
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1 vote
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### Collision-resistant single-pass EdDSA?

Is there any reason why collision resistant variants of ed25519 that use a single-pass aren't used instead? For example: $n = h(noncekey \| m)$ $h(R \| pub \| n)$ instead of $h(R \| pub \| m)$ or ...
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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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### Are SHA-1 hash collisions harder to find when files are big?

Was that just a coincidence, or did the 2 "shattered" pdf files whose SHA-1 hashes are identical had to be small in size (412KB) to make the collision attack easier?
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1 vote
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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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### 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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### Securely and Deterministically select a combination of objects from hash (cryptographic seed)

I am working on a project that is using a bit-commitment concept to authenticate information. I need to select a combination of objects securely from a secure hash, then distribute that hash later. ...
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1 vote