Linked Questions

1
vote
1answer
99 views

Are collision-resistant hash functions even possible? [see description] [duplicate]

Surely there can be no real collision resistant Hash function since hash values are of finite size which means there are finitely many of them, but there are an infinite number of messages we could ...
52
votes
2answers
15k views

What makes a hash function good for password hashing?

Using a cryptographic hash to store e.g. passwords in a database is considered good practice (as opposed to storing them plaintext), but is subject to attacks on said cryptographic hash, assuming the ...
6
votes
5answers
12k views

Would it be possible to generate the original data from a SHA-512 checksum?

So, I have a file that is XY Exabytes big. I create a SHA-512 hash from it. Are there any theoretical chances that I can retrieve the original data just from the sha512 hash? Also, are there any ...
4
votes
1answer
952 views

What gives SHA-256 its preimage resistance?

I was reading some guy's description of the SHA-256 algorithm and I noticed that the basic operations it uses appear trivial to reverse: addition, rotate bits, etc. When I say "reverse" I don't mean ...
5
votes
1answer
524 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
votes
1answer
402 views

help with cryptanalysis of a sponge permutation

I have been studying and researching hash functions. So far my research has led me to the sponge construction. It appears that the permutation used in the sponge to stir the state is more or less ...
1
vote
3answers
209 views

Would this hash functionality fall under pre-image resistance or collision resistance?

I understand that there are three main security requirements for hash functions, pre-image resistance, second pre-image resistance and collision resistance. I need to write about a hash function that ...
0
votes
2answers
204 views

What is the probability of the first half of a hash output being identical to the first half of another hash output?

Let's say for example that I encrypt a password with some hash function and receive a 256-bit hash value in return. What are the chances that the first 128-bits (half) of this value are identical to ...
4
votes
1answer
111 views

What is many:1 and collision in MD5?

This is in reference to this answer on Stackoverflow. If you read the first paragraph of the answer, you'll find this line: It's always a many:1 mapping (meaning there will always be collisions) ...
3
votes
0answers
354 views

Hash Function Properties

What i am trying to understand is shown in all three properties of secure hash function, i will focus on pre-image resistance. Pre-image resistance: given a hash h, it's difficult to find m s.t. H(m)=...
0
votes
2answers
126 views

Is there an outdated or insecure hash algorithm thats output can be easily reversed back into the input?

I'm looking for a hash algorithm thats output can be reversed back into the input in a reasonable amount of time (a day or less) using a decent consumer computer. If anyone has any information on this,...
1
vote
3answers
66 views

Can you find the salt if you have the original password in plaintext and the hashed version?

Suppose that I have a password in plaintext. I also have the hashed version of the password. Say it uses MD5. Is it possible to find out what the salt is given the above information? I'm guessing not?