Difficulty of finding an input string that hashes to a given value
12
votes
2answers
329 views
What is the general justification for the hardness of finding preimages for cryptographic hash functions?
Since most cryptographic hash functions are simple, compact constructions does this simplicity impose a limit on the complexity and the size of a function that can generate preimages? That is, given a ...
9
votes
1answer
184 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 ...
7
votes
3answers
1k views
What is pre-image resistance, and how can the lack thereof be exploited?
What is preimage resistance, and how can the lack thereof be exploited?
How is this different from collision resistance?
Are there any known preimage attacks that would be considered feasible?
3
votes
1answer
162 views
Is the last step of an iterated cryptographic hash still as resistant to preimage attacks as the original hash?
Considering a cryptographic hash, such as MD5 or SHA2, denoted by the function $H(m)$ where $m$ is an arbitrary binary string, there is a lot of material available that deals with potential weakness ...
2
votes
1answer
480 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 ...
1
vote
3answers
297 views
reverse of 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,
...
1
vote
2answers
123 views
Speeding up partially known plaintext preimage recovery attack on MD5
Suppose there are three messages A, B and C of different length, that are 16 DWORDs in ...
1
vote
2answers
199 views
Can one build a one-way function from AES?
We change the AES block cipher encryption:
we delete the key schedule algorithm
the user now provides a string of 1408 bits
we divide the string to 11 sub keys, and use them directly in the ...
0
votes
2answers
155 views
Finding partial pre-image of MD5 hash
I have the following requirement for hashing using MD5.
H(A,B,C,X);
Where values A,B & C are given. However X is not given.
I would like to find out what value of X would give a hash beginning ...
