Topic: DECENTRALIZED crypto currency (including Bitcoin) is a delusion (any solutions?) - page 32. (Read 91144 times)

Stellar's SCP consensus algorithm can be preempted forever by a Sybil attack (or it can be centralized where users trust those well known banks and such):

https://bitcointalksearch.org/topic/m.13778110

Following is written by David Mazières a PhD professor at Stanford who is the Chief Scientist at Stellar:


Again I maintain the Iota/DAG will only remain convergent with a centralization to enforce the trust math model. Btw, I will soon argue the same about Stellar as well.  

Stellar’s original system was modeled on one developed at the startup Ripple Labs, which is using it to help banks and other financial organizations move money faster (see “50 Smartest Companies 2014: Ripple Labs”).

Last year Stellar’s Ripple-consensus system unexpectedly “forked” into two networks that disagreed on which transactions were valid, and several hours’ worth of transactions got rolled back. Mazières says his new system avoids the part of the design that caused that problem.

The new SCP system also relies on people running software that communicates over the Internet, but trust is not enforced through mining. Instead, each person running the software must identify a few other trusted participants to correctly apply the cryptographic rules used to validate transactions. Each instance of the software will recognize transactions only once a certain majority fraction of its trusted partners have also signed off. And the trust relationships are all public.

Mazières says the math shows that those rules will allow his system to reliably verify transactions much more quickly and with less energy.

Dan Boneh, a Stanford professor who did not work on Mazières’s system but has reviewed it, says that SCP avoids some security limitations of Bitcoin. “The security proposition of Bitcoin is that the people who invested in mining infrastructure can be trusted, but that may not be true,” he says. “Here I can choose for myself who to trust.”

[...]

Emin Gün Sirer, an associate professor at Cornell University, agrees that SCP seems to have advantages over Bitcoin. He says it also seems to resolve what he considers a gap in the Ripple protocol that led to Stellar’s “forking” problem last year. “The protocol looks sound,” says Sirer.

It is, however, theoretically possible for SCP to break down if participants choose trusted partners in such a way that there aren’t enough overlaps to tie the network into one whole—or if an attacker orchestrates that situation, says Sirer. Just how unlikely that is will depend on the actions of the people who adopt SCP. “This is a social thing, not a technical thing,” says Sirer.

Mazières acknowledges that possibility but says it’s unlikely. He imagines that certain large organizations, perhaps banks, will emerge to anchor the SCP network. Still, he acknowledges, “people are always a weak point.”

Why are you spamming the thread! Fuck! Will you please stop this offtopic noise?

...and I have absolutely 0 fear of your partner's legal threats against me...

Lack of criticism about Iota makes me feel uncomfortable, you would do me a favor by "attack[ing] Iota in every thread".

Appears you are trying to bury the facts about Iota by spamming the thread.

I've warned you don't give me motivation to go on the offensive, because I can attack Iota in every thread. I haven't done that out of respect for you (and I have absolutely 0 fear of your partner's legal threats against me...rather I said I respected the attempt and the technical effort put into Iota, but that doesn't change the facts about it). Please be cordial and respect the desire to keep this thread S/N high.

It may be the case that no crypto currency can be decentralized. Keep that in mind.

My point is that you use "I don't want to repeat" too often. Now it looks as a trick to evade criticism. I think we all should wait until you post everything that comes to your mind. Post "Dixi" after that and lock the thread.

Please only post to add new information/refutation to this thread.

You've now succeeding in burying my important post (made less than an hour ago) upthread about Tendermint's flaws (my new research).

Add more pages of repeating the prior pages just adds more pages, thus you've made no point.

You expect people to read prior 33 pages? Hm, so you write all these texts just for the sake of writing? Ok.

Please I don't want to rehash the upthread discussion. We don't need to repeat ourselves again.

Again I maintain the Iota/DAG will only remain convergent with a centralization to enforce the trust math model. Btw, I will soon argue the same about Stellar as well.  

It's hard to (dis)agree with this because your definition of "centralization" is not clear.

AltcoinUK, the problem is that most readers do not understand the CAP theorem conceptualization of consensus problem nor will most users understand that Iota is based on a mathematical model that has to be enforced on all payers on their choices of which branch to attach their txns and on recipients in terms of what recipients compute is a probabilistically confirmed txn. If the Monte Carlo math can be enforced then consensus should converge, but there is no way to force decentralized actors to follow one math model when the system can't enforce it without centralization. Thus I stated Iota/DAG only converges if the system centralizes. As opposed to Satoshi's PoW which always converges because of the longest chain rule.

So it is extremely difficult to take an aggressive position when most readers won't even comprehend. Why is a speculator going to trust my assessment when they can't understand or don't have the attention span to digest my 33 page thread on Decentralization. Also I haven't written a white paper yet, so all that is not well formalized.

Arguably, ripple only works because ripple labs own the 5 validating nodes which control the network.

https://validators.ripple.com/#/validators

Again I maintain the Iota/DAG will only remain convergent with a centralization to enforce the trust math model.

There are a lot of things that can work in the real world but not in the ideal one. For example, Ripple.

There are a lot of things that can work in the real world but not in the ideal one. For example, Ripple.

Still another approach to consensus is Byzantine agreement [Pease et al. 1980; Lam-
port et al. 1982], the best known variant of which is PBFT [Castro and Liskov 1999].
Byzantine agreement ensures consensus despite arbitrary (including non-rational) be-
havior on the part of some fraction of participants. This approach has two appealing
properties. First, consensus can be fast and efficient. Second, trust is entirely decou-
pled from resource ownership, which makes it possible for a small non-profit to help
keep more powerful organizations, such as banks or CAs, honest. Complicating mat-
ters, however, all parties must agree on the the exact list of participants. Moreover,
attackers must be prevented from joining multiple times and exceeding the system’s
failure tolerance, a so-called Sybil attack [Douceur 2002]. BFT-CUP [Alchieri et al.
2008] accommodates unknown participants, but still presupposes a Sybil-proof cen-
tralized admission-control mechanism.
Generally, membership in Byzantine agreement systems is set by a central authority
or closed negotiation. Prior attempts to decentralize admission have given up some of
the benefits. One approach, taken by Ripple, is to publish a “starter” membership list
that participants can edit for themselves, hoping people’s edits are either inconsequen-
tial or reproduced by an overwhelming fraction of participants. Unfortunately, because
divergent lists invalidate safety guarantees [Schwartz et al. 2014], users are reluctant
to edit the list in practice and a great deal of power ends up concentrated in the main-
tainer of the starter list[i.e. centralized!]. Another approach, taken by Tendermint [Kwon 2014], is to
base membership on proof of stake. However, doing so once again ties trust to resource
ownership.

Following is written by David Mazières a PhD professor at Stanford who is the Chief Scientist at Stellar.

Incorrect! Tendermint is flawed and is a divergent non-consensus design that will crash and burn in the real world.

6. Consensus

6.1 On Byzantine Consensus

Fischer et al have shown in a seminal paper [9] that in an asynchronous
system (where no assumptions are made about time) of deterministic processes,
no protocol can guarantee consensus even with one faulty process. This is called
the FLP impossibility result. Much research has gone into understanding ways
to circumvent the FLP impossibility result by slightly modifying the problem do-
main, e.g. by sacrificing determinism, adding time, adding oracles etc [10]. Bitcoin
circumvents the FLP impossibility result by making some assumptions about the
synchrony of the network (i.e. nodes soon sync up with the network) and time (i.e.
miners dedicate limited time and resources to the best blockchain).
Our algorithm is based on algorithm 2’ from section 4 of [4] (Dwork et al).
It assumes that the network is partially synchronous; there is assumed to be some
unknown upper bound on the time of messages to be delivered. Intuitively, there
may be arbitrary but finite latency in the network. We also assume that all non-
byzantine nodes have access to an internal clock that can stay sufficiently accurate
for a short duration of time until consensus on the next block is achieved. The
clocks do not need to agree on a global time and may drift at some bounded rate
relative to global time. The algorithm is adapted to work with blockchains on a
gossip network. As in the algorithm proposed by Dwork et al, it can tolerate of up
to 1/3 byzantine voting power.

8. Conclusion

Tendermint is awesome. The future is now.

Thanks for attempting to make the readers misinformed. That will help prevent anyone from seriously implementing before I do. A future white paper can put this issue to rest.