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Some cryptocurrencies use fixed values in some positions in the resulting hash, like a fixed amount of initial zeros. What fixed positions and fixed values are Facebook Diem using?

David Jonsson
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    Are you speaking about proof-of-work? – Ievgeni Jul 05 '21 at 13:36
  • I wan't to know more about how secure it is. The more fixed values the less variation and less security in the algorithm. – David Jonsson Jul 05 '21 at 13:49
  • @Ievgeni Yes this is what is commonly called proof-of-work. I am interested in general how proof-of-work limits the hash function. – David Jonsson Jul 05 '21 at 15:05
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    Actually the leading zeros are more of a side-effect. Mostly it's just that the hash value must be less than a specific value (like $2^{256}/difficulty$). Of course that results in the first digits beeing zero. (but allows for smoother steps) – jjj Jul 11 '21 at 23:06

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As far as I understood, you are speaking about proof-of-work. But contrarily to what your question said :

Some Crypto currencies use fixed values in some positions in the resulting hash.

It corresponds to proof-of-work. The idea is the following, to guarantee that people which valid a transaction are "real", the have to solve a puzzle, which is basically a preimage of $\{0\}^\lambda\times\{0,1\}^{256-\lambda}$ for a specific hash function (parametrized by the transaction) (you can look this to have more precision : Complexity of Hash mining/signing)

But not all the cryptocurrency are using proof-of-work. And in particular, as far as I understood it's not the case for DIEM

Citation in the white-paper: "Second, this class of consensus protocols enables high transaction throughput, low latency, and a more energy-efficient approach to consensus than “proof of work” "

Link : https://www.diem.com/en-us/white-paper/#the-libra-blockchain

Citation in "The Libra Blockchain" paper:

"To do this, we plan to gradually transition to a proof-of-stake":

https://diem-developers-components.netlify.app/papers/the-diem-blockchain/2020-05-26.pdf

Ievgeni
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