Hacker News new | ask | show | jobs
by Buttes 3179 days ago
>what would happen to all credentials once issued to some blockchain, if that blockchain ceases to operate? The raw blockchain data is of course still available and maintains its blockchain structure. Yet the integrity-preserving features of the blockchain disappear as soon as it is no longer actively used.

I'm not sure this is true. Info about the blockchain wouldn't evaporate instantly, it'd be easy to get the legit genesis block header and chain height, wouldn't it require a lot of "work" to produce a convincing counterfeit chain?
2 comments
KirinDave 3179 days ago
No. It'd require only slightly more work than the cost of generating a block at that time, to generate a new plausible block altered arbitrarily.

The power of the "head" of the blockchain is the human consensus around it. It is otherwise unprivileged.

link
DennisP 3179 days ago
As with any transaction on a proof of work chain, the more work there is layered on top of the item in question, the more confidence you can have. Even if you don't know that someone's presenting you with a truncated chain, you can still see that their credential is at the end of it, and know that they could have cheaply faked it.

Proof of stake would require more human consensus but proof of work is measurably expensive to produce.

link
KirinDave 3179 days ago
> As with any transaction on a proof of work chain,

Only active proof of work chains. Discontinued chains have no active, competitive consensus and may be arbitrarily rewritten by attackers since there is no competition at any historical point in the chain for a quick mining operation and there is no consensus about the head of the chain.

If there are additional credentials and signatures embedded in the chain (there need not be) then THESE are the trust tokens that have value after the chain is discontinued.

Blockchains only offer one thing: human consensus when humans are not necessarily inclined to reach it. That is what a PoW or PoS blockchain algorithm for cryptocurrency is trying to guarantee.

link
DennisP 3178 days ago
You can still measure the total amount of hashpower applied. Someone could add arbitrarily many blocks but you can calculate how much it cost for them to do it.
link
KirinDave 3178 days ago
So? Without competition for time it's pretty easy to make quite long blockchains.

It's the competition for time that makes the mining reliable right now.

link
psyc 3178 days ago
I'm struggling to pinpoint where you two are talking past each other. "Length" in the context of a blockchain refers quite specifically to the amount of actual work. So "easy" to make "long" chain, seems like a straightforward contradiction.
link
DennisP 3178 days ago
The competition works by increasing the difficulty. At any given time there's a maximum numerical value of the block hash; the lower it is, the more hashes you have to make before you find a valid one.

The difficulty can be checked after the fact, by simply checking the numerical values of hashes. If a hash is one in a trillion, you know it took about a trillion attempts on average to make it, and you can figure out the economic cost of doing that.

It would be easy to make a chain with lots of blocks of low difficulty. It would also be easy for anyone to see that it didn't cost much to make it.

link
ringaroundthetx 3178 days ago
yes that is interesting, it is the same as one copy of the database. you would have to find someone mirroring another copy and compare them.

if we live in a world where one-copy is fine most of the time, then this is a marginal improvement adding just a little redundancy between unknown parties.

some kid with the blockchain copy in their temp folder from years before will save the key pairs for humanity.

link