3) Same question for Ripple
I have read that Ripple "transaction validators" don't need prior "ledgers" to operate, they just sign current ones and not necessarily store previous ledgers (in fact ledger before #32570 is already lost and not "recoverable", someone says.)
They claim they solved "scalability problems" by adopting this method and many people say Ripple does not use "Blockchain" technology.
That's actually a problem currently - there is no server on the network that has any ledger before 32570 (the older ledgers got corrupted in "ye olden days" and nobody got around to fixing them). ...
(
https://forum.ripple.com/viewtopic.php?f=1&t=4717&f=1&t=4717#p28026)
Btw, regarding consensus technology (which is the most basic foundation of crypto and the most important part, I think),
I found that Nxt's algorithm is super-cool.
Here is the graphical inspiration: (
http://nxtportal.org/forgers/)
[Re: Concise but complete technical description of various proof-of-stake (PoS) schemes?]
(Come-from-Beyond says:) The software determines the best chain by analyzing ratio of transactions belonging to well-known participants (e.g. Walmart, Alibaba, Coinbase) of the economical cluster using Nxt. Non-legit chains can't include such transactions because every transaction refers to a block mined several minutes before the transaction timestamp, which prevents inclusion of majority of the transactions into chains with lower cumulative difficulty or into chains generated by an adversary.
(
https://bitcointalk.org/index.php?topic=1012241.msg10987520#msg10987520)