Questions tagged [2nd-preimage-resistance]

Difficulty of finding another input string that hashes to the same value as a given string

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1answer
29k views

Second pre-image resistance vs Collision resistance

From Wikipedia: Second pre-image resistance Given an input $m_1$ it should be difficult to find another input $m_2$ such that $m_1$ ≠ $m_2$ and $\operatorname{hash}(m_1) = \operatorname{hash}...
19
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2answers
4k views

Why is Pearson hash not used as a cryptographic hash?

The original algorithm produces 1 byte long hash and is (of course) not suitable for cryptography use. But according to wikipedia, it is possible and easy to produce Pearson hash of any length, simply ...
19
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3answers
798 views

Collision or second preimage for the ChaCha core?

Daniel J. Bernstein's ChaCha core is an evolution of the Salsa20 core. Both are functions over the set of 512-bit bitstrings, partitioned as sixteen 32-bit words. Can we exhibit collisions, or second-...
18
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1answer
10k views

Does collision resistance imply (or not) second-preimage resistance?

I've seen contradictory results. Sometimes hash functions are collision-resistant but not necessarily second-preimage resistant. I've seen this kind of things in papers from Bart Preneel: “Security ...
17
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2answers
7k views

Pre-image resistant but not 2nd pre-image resistant?

Are there any cryptographic hash functions for which there is a known pre-image attack, or a known second pre-image attack, but not both? The attack doesn't have to be practical - just anything that ...
13
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2answers
7k views

Why does second pre-image resistance imply pre-image resistance

I am studying hash functions. I can understand why collision resistance implies second preimage resistance, but I don't get why second preimage resistance should imply first preimage resistance. Could ...
13
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1answer
5k views

Is a second preimage attack on MD5 feasible?

What's the practical status of MD5 w.r.t. second-preimage? Integrity of a piece of data is protected by an MD5 hash, itself assumed genuine. The data (and thus the hash) is known to the adversary. ...
12
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3answers
2k views

SHA3-255, one bit less

I need a SHA3-255 or 511. What if I simply truncate a standard SHA3-256 or 512? Apart from the doubled probability of hash collision, are there any other things I should be aware of? I could also ...
11
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1answer
3k views

Why doesn't preimage resistance imply the second preimage resistance?

Let the preimage resistance be defined as »given a hash value $h$, it is hard to find any message $m$ such that $\operatorname{hash}(m)=h$«, and let the second preimage resistance be defined as »given ...
11
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1answer
567 views

Which MACs can be converted into a secure unkeyed hash function?

It is known that setting the secret key to a fixed, public value does not make MACs like CBC-MAC or GMAC into secure unkeyed cryptographic hash functions that could be used - for instance - for ...
10
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1answer
3k views

Is MD5 second-preimage resistant when used only on FIXED length messages?

I fully realize that MD5 should not be used in any new project, but in my particular situation I have severe CPU performance issues, so MD5 is convenient. I have read a lot about MD5 security for this ...
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3answers
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The difference between being not strongly collision resistant, and not weakly collision resistant?

So I understand the two concepts: (Strong) collision resistance: it is infeasible to find a pair $x \neq x'$ such that $h(x) = h(x')$ Weak collision resistance / 2nd-preimage resistance: for all $x \...
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2answers
3k views

Why might SHA-384 throughput be lower than SHA-512 throughput in hashcat and more secure?

I found a hashcat benchmark results in the internet: hashcat results: SHA-384 is 17065.4 MH/s SHA-512 is 17280.3 MH/s Why does SHA-512 take less time? SHA-512 is longer and I thought it therefore ...
6
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2answers
16k views

Computational requirements for breaking SHA-256?

Let's define "breaking" a hash function $H$ as being threefold (corresponding to the main properties of a cryptographic hash function): preimage attacks to get $m$ knowing $H(m)$ second-preimage ...
6
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2answers
922 views

Is there a feasible preimage attack for any hash function (no matter how deprecated) today?

Has there ever been a hash function that was actually used in the field, no matter how long ago, for which there is now a feasible preimage attack? All hashes that are nowadays considered 'broken' (...
6
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1answer
161 views

Has there ever been more then a theoretical difference between preimage resistance and second preimage resistance?

In other words, has there ever been a point in time in which having the content of a message has actually helped break a hash function?
6
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1answer
586 views

Fast 128-bit MAC with second preimage resistance?

I have an application that needs a fast 128-bit MAC to guarantee message authenticity in a protocol. I would like to reuse this MAC value as a binding identifier, so that even those who know the key ...
5
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1answer
1k views

Functions that are only second-preimage resistant?

Are there functions that satisfy the second-preimage resistance property without satisfying the others (preimage and collision resistance) ? I'm looking about such functions that compress data (exit ...
5
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2answers
224 views

usefulness of a collision attack that's not also a 2nd pre-image attack

So my understanding is that if we've got some hash function $H$ then a 2nd pre-image attack is one where given a message-hash pair $(m, H(m))$ we can find some $m' \neq m : H(m') = H(m)$, while a ...
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2answers
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Are My Answers to This Hash Question Correct?

Question When determining the security of a hash system, the cryptanalyst tries the following attacks. (a) If the attacker is NOT allowed to modify the original message, determine the number of hash ...
4
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1answer
1k views

Is $H(x) = x^2 \bmod p$ pre-image resistant, second pre-image resistant and/or collision resistant

I have the function $H(x) = x^2\bmod p$ , where $p$ is a prime of length n bits and this function maps to the message $x$ to a n-bit hash value $H(x)$. I need to find out if it is pre-image resistant,...
4
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2answers
4k views

Difference between collision resistance and target collision resistance

For a hash function, what's the difference between Collision Resistance and Target Collision Resistance?. I understand the definition of hash function collision resistance, but I don't know about ...
4
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1answer
753 views

How can I determine if a hash function is secure?

I'm doing an exam in computer security and I encountered this problem which I'm unsure of how to attack properly. Should I get down and dirty with the Hash function on paper or is there a more general ...
4
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1answer
851 views

Why do different applications of hash functions demand different properties of the hash function?

A strong cryptographic hash function in general must guarantee several properties, including: Preimage resistance, second preimage resistance and collision resistance. It turns out, however, that ...
4
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1answer
343 views

Why this isn't second preimage resistance?

I've been reading on preimage resistance and trying out few examples for the same and I'm trying to figure out why the following hash function does not have the second preimage resistance and any ...
4
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1answer
261 views

Effect of message length on collision attacks

I know that message collisions are supposed to be hard to calculate for a good cryptographic hash. Given 1k worth of data, it's hard to find another 1k worth of data that collides with the same hash. ...
4
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1answer
181 views

Converting a pre-image resistant hash to second pre-image resistant

I am looking for some standard conversion from any hash function $f$, which has pre-image resistance, to another hash function with second preimage resistance. Is there such a standard conversion?
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0answers
236 views

Second preimage attack complexity when the digest is malleable

An attacker has a hash $h$ and a message $m$. He wants to find $m^\prime$ with the same length as $m$ which hashes to $h^\prime$. However, $m^\prime$ can only differ from $m$ in the 1 bits (i.e. ...
3
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3answers
913 views

Computational feasible to reverse MD5SUM?

This might be out of ignorance, I apologize, but how complex of a problem might it be to generate a file of size $N$ whose MD5SUM is $X$? For example, ...
3
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2answers
444 views

What, cryptographically speaking, is a "long message"?

I have read about long message attacks on some cryptographic hash functions. However, I don't quite understand what is being referred to as a "long message". Also, do long message attacks only apply ...
3
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1answer
775 views

Difference between second pre-image resistance attack and collision attack

According to my understanding of hashing algorithms -: Collision attack is an attack wherein we have a hash(x) and we try to find hash(y) such that x!=y while hash(x)=hash(y). Second pre-image ...
3
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1answer
938 views

Winternitz One time signature security

There are two versions of Winternitz-One time signature scheme, $W-OTS$ and $W-OTS^+$ Security of both is as following $W-OTS$ is strongly unforgeable under chosen message attacks if $F$ is a ...
3
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1answer
1k views

Difficulty of collision vs preimage vs second-preimage attacks

It seems at first glance that brute-forcing a collision would be exactly as difficult for all of them. They all (I would expect) work like this: select a hash value, and then try messages to get an ...
3
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2answers
128 views

Application of cryptographic hash functions which do not require collision resistance property

I can not understand why collision resistance of a cryptographic hash function is not required for some applications. for example, if we store the trusted hash of a file or program, and later when we ...
3
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1answer
102 views

Security implications of slow-by-design hashes on relative security vs. hash size

Would it be true to say that that one can get away with much smaller cryptographic hashes if the hashing algorithm is slow and expensive by design? Example: let's say you want 128-bit hashes. This is ...
3
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1answer
287 views

Does SipHash have 64 bit (second) preimage security?

I was not able to find an explicit statement about the first and second preimage security of SipHash-2-4 or SipHash-4-8 anywhere. I think it should be 64 bits, but I'd feel safer if somebody who has ...
3
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1answer
446 views

Increased security weaknesses when truncating SHA1

Given the following preconditions: A plaintext A (~512bit length), that is hashed by using SHA-1 and truncated to (the first) 64 bits. I know both, the plaintext and the truncated hash, and want ...
3
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1answer
201 views

Do hash functions for digital signatures need to be preimage resistant?

I understand that hash functions used for hashing a document or some data before signing it, needs to be collision resistant and 2nd pre-image resistance. Otherwise an adversary could "look" ...
3
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0answers
24 views

How to find k-way second preimages

For example: Assuming someone has found a second preimage for SHA-256. In other words, for SHA256(M1)=H, someone has found M2 which SHA256(M2)=H Now, is it possible to generate k-way second ...
3
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0answers
2k views

Example of second preimage attack [closed]

Please, I'm trying to understand second-preimage attacks on cryptographic hash functions. I understand the definition well: given a message and it's hash, an attacker finds another message which ...
2
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2answers
569 views

collisions on hash functions

Why do we say that collision-resistance is a "harder" property than second pre-image for hash functions whereas if you have an attack on the second pre-image then you find a collision ? Moreover, a ...
2
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1answer
289 views

Practicality of a certain hash function

Consider the following hash function: $$(V\cdot A + V\cdot B)^2 \bmod C$$ $A, B,$ and $C$ are large primes. $V$ is the value to be hashed and is guaranteed to contain at least as many bits as the ...
2
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1answer
491 views

Hashing based on the discrete logarithm problem

At a first look, one could use the elliptic curve discrete logarithm problem to grant for the onewayness of $H(x)=x*G$ (where $G$ is the generator point of the cyclic subgroup). Additionally, $H(x)$ ...
2
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1answer
538 views

What is the complexity to break second preimage resistance?

In the context an of hash functions we have three required properties. Preimage resistance Second preimage resistance Collision resistance. The bounds for Pre image collision is $O(2^{n-1})$, the ...
2
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1answer
331 views

Explanations for the complexity values for second preimage attack on GOST?

I've been reading the article "A (second) preimage attack on the GOST hash function" by F. Mendel et al (link) and I'm having some difficulty to grasp some of the values of complexities/probabilities ...
2
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1answer
473 views

Hash-based signature scheme XMSS/LMS susceptible to preimage/second preimage attack?

Are the quantum secure hash based signatures (XMSS/LMS) susceptible to preimage/second preimage attack?
2
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1answer
84 views

What are the “costs” to find a pre-image, weak collision, or strong collision?

For a secure, n-bit hash function, what are the “costs” to find a pre-image, weak collision, or strong collision?
2
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1answer
123 views

Is an HMAC based on a second-preimage resistant hash function always unforgeable?

If hash function is collision-resistant, then its associated HMAC is always unforgeable. But suppose that a hash function is only second-preimage resistant, not necessarily collision-resistant. Then ...
2
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1answer
127 views

Cryptographic hash function based on logistic map?

Is there any secure cryptographic hash function based on the logistic map?
1
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1answer
310 views

Question about second preimage resistance of hash function combiner

Let $\Pi=(Gen_1,H_1)$ and $\Pi=(Gen_2,H_2)$ be two hash functions. Define $(Gen, H)$ so that $Gen$ runs $Gen_1$ and $Gen_2$ obtaining $s_1$ and $s_2$ respectively. Then let $H^{s_1,s_2}(x)=H^{s_1}(x)\|...