Why bother hashing?

[Dan]

I'm looking into block chain technology, and this question keeps coming back to me. For the sake of generality, lets say all the currency is already in existence, so mining a block no longer serves the purpose of creating currency.
What is it that requires the need to hash a block of transactions - why make it hard?

For example, if the entire network can verify a group of transactions by looking at previous transactions they have on their version of the ledger, and then agree on an average time-stamp for that group of transactions, I do not see the need for the 'proof of work'/hashing step.
What attack does hashing prevent, that this simple unhashed version of a block chain would not?

 

[satoshis_sockpuppet]

and then agree on an average time-stamp for that group of transactions,

How should they "agree" on something without a central authority?

 

[Dan]

Couldn't they agree the same way it is currently agreed upon? The process would be the same.

 

[satoshis_sockpuppet]

Yes, and the way they agree now, is by the most computational work done for ordering the transactions -> proof of work.

Another idea to reach the agreement ist "proof of stake" which Ethereum uses or plans to use (don't know the current stand). But you need something "behind" the ordering, else you can't decide which version of history is the correct one.

 

[Dan]

You could have some sort of system where every 10 minutes the nodes group all the transactions since the last block, and the winning block/consensus is determined by the most transactions in a group. Maybe there are some flaws in this specific method - I don't know - I just thought of something from the top of my head. The point is that hashing is not required for a consensus, which is proved by PoS.

What attack is hashing/proof of work stopping, that a system purely based on something such as PoS would not? It seems that PoW is a needlessly hard computational solution.

 

[satoshis_sockpuppet]

Maybe there are some flaws in this specific method

How would you determine, which history is correct, if you got a block with 10 tx and later you got a block from someone with 100 tx?

How would you distribute the coins if you use PoS?

If you talk about a switch after coin distribution: Some coins do it.
Start here: https://en.wikipedia.org/wiki/Proof-of-stake#Criticism

PoS vs. PoW is a topic for itself.

 

[Dan]

I really appreciate the time you've taken to answer some of my questions satoshis_sockpuppet, and I hope you can forgive my ignorance I think I will look more into PoW vs PoS.

So hashing is a solution to obtain a decentralised consensus of a history, that can not easily be changed, but there are alternatives.

 

[satoshis_sockpuppet]

No problem!

"So hashing is a solution to obtain a decentralised consensus of a history"
Replace "hashing" with Proof of work, but in this sense, yes.