[Cryptography] Our leader opines on cryptocurrencies
jamesd at echeque.com
jamesd at echeque.com
Sat Jul 20 23:32:05 EDT 2019
On 2019-07-20 12:56 pm, John Levine wrote:
> Master Card can process 38,000 transactions per second, and Visa about
> the same. Good luck doing that with a blockchain, even a closed
> non-PoW one.
Working on it:
Assume delegated proof of stake, in which the merkle patricia root of
the most recent block is signed by a quite small number of big peers on
the blockchain, each representing a very large number of very big
clients each owning a great deal of stake. (Ordinary clients are
insignificant. Ordinary peers are insignificant, but the interests of
big peers and big clients are aligned with those of small peers and
small clients, if there are enough of them.)
Then each big peer has to process about one hundred thousand
transactions per second, assuming we want to replace government fiat
currencies with a blockchain currency.
So we have a small number of peers, each peer processing the entire
blockchain, and each peer composed of a large number of shards, each
shard processing a shard of the blockchain.
Assume the processing is shardable with mutually trusting shards that do
not suffer byzantine failure.
The computer sitting under my desk, with a consumer grade fiber to the
curb connection to the internet, could probably process six thousand
transactions per second running four shards in a single physical
computer, so each peer is going to need forty such shards running on ten
such devices, say a eighty such shards running on twenty such devices
for redundancy and storage, each device having twelve six terabyte hard
disks.
The shards coordinate by non byzantine paxos on a single hash once every
few minutes, and the peers coordinate on a single hash by byzantine
paxos. The number of peers, and the number of shards, is small enough
that we don't hit paxos scaling problems.
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