Questions tagged [2nd-preimage-resistance]

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

Filter by
Sorted by
Tagged with
14
votes
2answers
5k 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
votes
1answer
4k 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. ...
11
votes
1answer
2k 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 ...
18
votes
3answers
604 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-...
11
votes
2answers
5k 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. ...
17
votes
1answer
7k 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 ...
30
votes
1answer
20k 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}...
9
votes
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 ...
3
votes
2answers
3k 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 ...
19
votes
2answers
3k 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, ...
4
votes
2answers
7k 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 ...
3
votes
1answer
792 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 ...
4
votes
1answer
164 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?
2
votes
1answer
359 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?
3
votes
3answers
819 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, ...