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0 pointsgtrubetskoy8y ago0 comments

Think of it this way: the block is the input to SHA. When the puzzle is solved, that block happens exactly at the time the puzzle is solved, and no one cannot dispute it. There is no other way (or at least none that I can think of) to link a pile of data to a point in time.

The only way you'd get this level of accuracy with a traditional clock is if you could measure/record Planck Time, which isn't possible and might never be. And if we could have Planck Time accuracy clocks, such a timestamp wouldn't come with a cryptographic proof like the PoW timestamp.

Everything else is secondary, an add on. The ordering is determined be the longest chain, recorded as a Merkle tree, transactions are tied by the strength of Elliptic Curve crytpography, miners motivated by rewards, etc.

But without that timestamp, none of it would work.

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danbruc8y ago· 2 in thread

Nope. You find a good hash at a specific point in time, but that is nothing special, every event happens by its very definition at a specific point in time. Committing a database transaction, potentially including finical transaction records, occurs at a specific point in time.

But that is all without consequences, nobody will know about this event until you broadcast and they receive your block. And the message about the new block will arrive at different nodes at different times. End if you are really inclined to pull physics into this - which in my opinion hardly makes any sense - you have to face the fact that simultaneity is relative.

So you are really not tying the discovery of the new block to any specific point in time. Everything anybody can really say is that it happened before they received the block and after the block that is referenced by the previous block hash was mined which itself may have happened any time before they first received that block.

The previous block hash establishes a happened before relation between the events of creating the blocks in the chain and including a transaction in a block establishes a happened before relation between the creation of the transaction and the creation of the block. But nothing ties anything to any specific point in time. And proof of work plays no role here at all, you can simply calculate a single hash of a block and send it to me and that proofs that the block existed before I received that hash, no need to work hard to find a fancy hash with many leading zeros.

gtrubetskoyOP8y ago

The valid sha ties this block to the exact point in time at which the solution was found. We can't know exactly what time in hh:mm:ss that was, but we do know the chain height, and the height is how "blockchain time" is told.

The fact that the block time (i.e. height) is when the conforming SHA was found is indisputable. Also that no other block happened at this same point in time.

danbruc8y ago

The valid sha ties this block to the exact point in time at which the solution was found.

It does not, it just sets a lower bound on the time. I can totally mine a block linking directly to the genesis block today. All it proofs is that it happened after the previous block was created. And so does SHA(<GenesisBlock>) without any mining.

Also that no other block happened at this same point in time.

Also not true, I can totally mine several blocks all linking back to the same block. And with some luck that might also happen at the exact same point in time.

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