[/b] How was satoshi able to solve this?[/b]
Satoshi was able to solve this big economic issue by introducing a decentralized public ledger that relies on a proof of work algorithm to establish any valid consensus.
um, no.
Proof of work. is not the consensus. its just the proof of expense of hard work for formulating a difficult ID for a block of data. that is all.
blockchains can use many algo's(proofs) for the hardening of the ID
the ID identifies the data within. thus any changes to the data changes the ID. so making it expensive to make an ID makes it expensive to change the data
PoW is just the most expensive proven method of hardening batch of data. making it multiply the expense the further you go back to change it and then rush forward by 5 blocks (6 total) now to overtake the network
good network gA gB gC gD gE gF
malicious user gA bA bB bC bD bE bF
to get bG to be seen before gG to then make everyone adopt bA bB bC bD dE bF and drop gA gB gC gD gE.. malicious user has to be faster than the entire good network just to be able to work on his bA variant and then catch back up and overtake ~6 blocks later
which is why they say 6 confirms is deemed safe.(someone has to be considerable even faster then good network for less than 6 confirms)
but he cant change the rules. or algo. all he can achieve is changing the data in the blocks
(remove/change transactions in A B C D E F)
consensus and consensus changes is not determined by PoW. PoW is just to make it expensive to change the transaction order (unspend an already spent transactions). consensus determins what rules are implied. where one rule is that it can use PoW. but consensus change could(but shouldnt) decide to change to a different Po?. .. the PoW does not determine consensus. consensus determines PoW
the consensus. is a bunch of rules all users should equally follow. where by anyone not following the rules . ends up outside the network.
because anyone not following the rules is just making THEMSELF ignorant to the rules/data and making only themselves blind to the network
if bA contained weird data breaking the rules the good network would reject it. making malicious users efforts for nothing.
all malicious user can do is just change which transactions are included in a block. where the selection has to still fit within the rules
Which means nothing on the network is hidden and no process can be undone since tampering with a single data on the blockchain will affect every other entry down to the genesis block rendering the whole database void and all this approach don't need a central authority to decide which data comes first rather than a consensus of the nodes on the network even satoshi himself doesn't have autonomy over the network what a selfless service
there is a process to undo blocks. but all you can achieve from this is changing what transactions to remove/include in new block list.
PoW just makes it too expensive to attempt it.
EG to do the edit, it costs $200k to solve a block and requires 6 blocks ($1.2m) then overtake the network to get people to follow your chain of blocks
why remove your $3 coffee purchase from the chain if its going to cost you $1.2m to get it seen as no longer on the majority chain
thus its not worth changing things for a $3 refund.again hense why 6confirms are safe for value upto $1.2mill
to change the rules. well no single person can try that. as it requires the majority collectively to follow any new rules for that new rule to be accepted
the consensus rules are HARD strict about whats valid. the consensus of HARD rules only change when majority all agree. and its then determined safe to activate a new rule, and thus everyone follow the new rule after an agreed event.. any minority disagreement means the minority are rejected. the rules only become enforced when its a known point that majority want the new rules and deemed safe to activate a new rule because its deemed safe that majority will be able to follow the new rules.
without majority. there is no point trying new rules because if only a minority are following. then that minority will just get rejected by the majority following normal rules.
some soft rules can be changed without controversy(like blindly accepting a transaction of unknown format) but that just makes the user that does not understand the format blindly accept something unchecked. which makes them waste their effort pretending to be a full validator/checker
