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7 votes

SHA3-256 vs SHAKE256_256 in XMSS and SPHINCS

What is the motivation of choosing SHAKE256_256 instead of SHA3-256 in XMSS and SPHINCS. For Sphincs+ (SLH-DSA), sometimes there is a need to generate more than 256 bits from a single hash operation; ...
poncho's user avatar
  • 145k
3 votes
Accepted

What's the name of the property of ideal cryptographic hash functions that effectively make it a random number generator?

I believe you are looking for the concept of 'indistinguishability'. Boneh and Shoup mention it when they discuss the 'Message Integrity' construction in their book A Graduate Course in Applied ...
Crypto Learner's user avatar
1 vote

Is it possible to deduce the input of a hash by running in reverse?

Yes, you could in principle do something like this, but how many steps becomes prohibitive (too expensive) to continue reconstructing a hash original data input? will be a quite small number. I'll ...
Mark's user avatar
  • 11.6k
1 vote

What's the name of the property of ideal cryptographic hash functions that effectively make it a random number generator?

I second the other answer: "indistinguishability" (from a "random oracle" or a "random function") is the name of the property thought. Addressing the last question: ...
fgrieu's user avatar
  • 138k
1 vote
Accepted

Proof of work for large amount of data

If you want to determine whether a file has undergone format conversion, I'd venture that no algebraic approach (such as squaring over integers modulo $p$) is likely to be directly useful. Assume the ...
kodlu's user avatar
  • 21.2k
1 vote

Why cant you use randomness to seed more randomness?

Why cant you use randomness to seed more randomness? Obviously you can, that's what any (Cryptographically Secure) Pseudo Random Number Generator or (CS)PRNG does after all. Could the resulting hash ...
Maarten Bodewes's user avatar
  • 91.7k
1 vote

Pre-image resistant but not 2nd pre-image resistant?

Great answers here already! That said, the specific example given in Reid's answer kind of confuses my brain. So, here's a really simple example, to help out anyone else in the same boat. Take any ...
SocraticMathTutor's user avatar

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