A cryptographic hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm makes it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.
2
votes
1answer
203 views
What happens to the entropy of a password when you hash it?
For example, if the entropy of a password is 30 bits, what is the entropy of the password when you hash it with MD5?
2
votes
1answer
95 views
Why are there $ signs in my passwd file?
I am trying to get access to my eReader and I managed to get the passwd file.
...
1
vote
1answer
60 views
Why are the Davies-Meyer and Miyaguchi-Preneel constructions secure?
The Davies-Meyer compression function $h(H, m) = E_m(H) \oplus H$ is said to be secure. So too is the Miyaguchi-Preneel compression function $h(H, m) = E_m(H) \oplus m \oplus H$. Why are these ...
1
vote
2answers
122 views
Store hashed email and compare hash values
I have a number of different systems sending me email addresses, but I don't actually need the underlying email, just a hash of the email address. I know I can compare hash values to find matches ...
1
vote
1answer
186 views
How do unkeyed hash functions (for MDCs) provide security?
Unkeyed hash functions are, by definition, hash functions computed without a key. SHA-1 is an example. MDCs (message digest codes) are a subclass of unkeyed hash functions. How are unkeyed hash ...
1
vote
1answer
283 views
How to implement order preserving encryption or order preserving hashing
Does anybody know any free implementation of either order preserving encryption or order preserving hashing? I've found some codes like CMPH but I need to dynamically add new DATA and that's why most ...
1
vote
3answers
304 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,
...
0
votes
2answers
203 views
SHA-1:Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output?
Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that a 160-bit SHA-1 hash output contains at least 128 1's?
