Linked Questions

95 votes
2 answers

What is the "Random Oracle Model" and why is it controversial?

What is the "Random Oracle Model"? Is it an "assumption" akin to the hardness of factoring and discrete log? Or something else? And why do some researchers have a strong distrust of this model?
Fixee's user avatar
  • 4,128
18 votes
3 answers

Why do "nothing up my sleeve numbers" have low entropy?

As a preface, forgive me for some of the links being from Wikipedia. I realize that academia frowns upon this. I came across this article about "nothing up my sleeve numbers". In it, it says: In ...
asteri's user avatar
  • 283
6 votes
2 answers

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 ...
sluge's user avatar
  • 197
10 votes
2 answers

Which attacks are prevented by the different initial hash values for SHA-2 with truncated output?

NIST specified SHA-2 hash functions with truncated output. Those hashes use different initialization values than SHA-256 or SHA-512. SHA-224 is based on SHA-256. SHA-384, SHA-512/224 and SHA-512/256 ...
Maarten Bodewes's user avatar
  • 91.8k
8 votes
1 answer

Does "SHA-256/192" use different initial values from SHA-256?

I've seen some mentions of a "SHA-256/192" online. Clearly, this means the output of SHA-256 is truncated to 192 bits, but does it also use different Initial Values like SHA-512/256?
Myria's user avatar
  • 2,513
4 votes
1 answer

Is KMAC just SHA-3-256(KEY || message)

According to keccak strengths you have: Unlike SHA-1 and SHA-2, Keccak does not have the length-extension weakness, hence does not need the HMAC nested construction. Instead, MAC computation can be ...
Finlay Weber's user avatar
4 votes
2 answers

how to use these hash functions in python?

In this article, specifically in the section 4.1 of the initialization phase,the following cryptographic hash functions have been chosen: \begin{align} ...
Chai Ma's user avatar
  • 125
2 votes
2 answers

Verifying a prediction of the future

I'm trying to find an algorithm to prove that someone knows some short secret message (for example some prediction of the future) before finally revealing it. For example: Alice knows what temperature ...
svm's user avatar
  • 23
4 votes
1 answer

Applications in which you should/shouldn't use a salt with HKDF

rfc5869 has the following to say about the use or lack thereof of salts with HKDF: HKDF is defined to operate with and without random salt. This is done to accommodate applications where a salt value ...
nohatsatthetable's user avatar
1 vote
3 answers

Using date stamp down to milliseconds / ticks as a salt?

As I understand it, the salt is used to ensure that a hash of two of the same strings results in a different hash. The salt is often stored with the hash, either prepended or as a separate field. As ...
RemarkLima's user avatar
2 votes
1 answer

are outputs of sha256 independent when padded with different seed each time, in other words, when inputs can be somewhat related

So I was wondering about what will be the dependence of the outputs when I padded one input with two different strings two times for technically generating two different strings, say the input string ...
Subha Nawer Pushpita's user avatar
1 vote
1 answer

Do people manually select every integer used in a crypto hash function or are they generated by a computer?

For example, this: Are all those numbers like 7, 4, 13, 1, 10, 6, 15, 3, 12, 0, 9, 5, 2, 14, 11, 8... picked by hand somehow, or are they just selected out of a ...
Lance's user avatar
  • 171
0 votes
1 answer

Different inputs but able to generate consistent outputs across different SHA engines

Say I'm feeding in few thousand bits data (INPUT AAAA) into both SHA256 & SHA3 256 engines at the same time. (Both engines using different hashing architecture) and hence it will generate ...
Pi-Turn's user avatar
  • 83
1 vote
1 answer

Use of HKDF to get shorter key than digest size

Is OK to derive a key using HKDF (Extract & expand) with a shorter size than the digest size of the configured hash function? In that case the result is computed (on the expand part) by truncating ...
carce-bo's user avatar
  • 195