Topic: DECENTRALIZED crypto currency (including Bitcoin) is a delusion (any solutions?) - page 10. (Read 91140 times)

I just stumbled upon Solidus, a proposed Cryptocurrency based on permissionless Byzantine Consensus:


Solidus uses PoW for leader election to adapt the Practical Byzantine Fault Tolerance (PBFT) protocol to a permissionless setting. It comes with a whole set of incentive
mechanisms for different kinds of actions. As far as I can tell, it's far more sophisticated than BitcoinNG and ByzCoin and (promises) offers quite some advantages over them. However, it still relies on the assumption that at least 2/3 of the computing power is controlled by honest nodes.

In summary, this work presents Solidus, a scalable and incentive compatible cryptocurrency based on a fault-tolerant committee and permissionless Byzantine consensus. It is secure against withholding attacks such as selfish mining and provides instantaneous confirmation of transactions. Perhaps a limitation of Solidus is that the protocol is currently rather complex. It remains interesting future work to simplify and improve the Solidus protocol.

Btw, if you are wondering how my design solves the Scalepolcapyspe winner-take-all power vacuum problem of crypto-currency:

Homeostasis

Don't get overly excited about Teechan:

Aren't we trusting that the manufacturer's key (for the endorsement certificate of the attestation key) isn't compromised or given away to for example the NSA?

Also apparently there may be some hidden licensing capability in SGX.

The last paragraph of section 6 Related Work in your paper explains that you've done nothing to solve a routing network which is the one of the main insoluble flaws of LN because it will only scale with centralization, so it is disingenuous or slightly confusing to imply in this blog (from the perspective of unsophisticated readers) that your invention can be used to do anything remotely useful with Bitcoin as it is today.

Also payment channels do nothing for real-time blockchain updates for features other than payments, such as Steem(it)'s social networking on a blockchain updates. Payment channels are a narrow application of a blockchain.

Good point. Their requirement is basically one of requiring external synchronization, but asynchrony is the norm on networks. Synchrony is generally impossible.

I added the following edit to my comment at Medium:

There are many cases where you might see conflicting transactions in the network that we're broadcast legitimately by honest users.

An obvious one that springs to mind is a company that has a number of nodes across the planet and is processing payments in some form.  If one (or more) of the nodes are subject to some lag, they might create and broadcast a payment that already exists via some smart-contract logic perhaps, yet the producing node is not aware of it being a duplicate due to lag (or any other reason).

That's not being dishonest and is a legitimate case that can, and will happen.

Edit: Fuserleer (eMunie developer) has pointed out that this requires external synchronization which is generally impossible on networks, e.g. wherein a company has multiple nodes across the network which issue transactions asynchronously. Thus employing the blockchain as the synchronization mechanism. If the company tried to employ their own blockchain for synchronization, then forwarded the transactions to your blockchain, then it requires one node to synchronize to do the forwarding, which is not resilient. In general, asynchrony can’t be avoided.

My off-the-top-of-my-head quick list of issues with SPECTRE:

https://medium.com/@shelby_78386/quoting-from-the-whitepaper-29e9fbc0ebec#.f4n0rdaho

Afaics, this fundamental assumption which your design hinges on, does not work in a crypto-currency system.

What if a user needs to increase the transaction fee paid because none of the miners are including the transaction?

But you are arguing that the attacker doesn't need a majority of the historic private keys (to overcome TaPoS), so therefor the number of attackers are unbounded. Thus there is no objectivity between unbounded forks. Thus of course the current stake holders must refuse, lest their entire stake be worthless.

It can’t be irrefutably proven that the 3 malevolent marbles were cheating because they can each claim that other one became unresponsive when they each separately vote for one of the conflicting quorums; thus the justification that voting for more than two quorums became necessary. And the honest marble voted more than twice also or became unresponsive, so the 4 voters are all ambiguously malevolent from the perspective of any observer.

Nope, sorry.

Any graphs to help me?

The second reformulation of BFT has been proven for ≥ (N + 1)/2 (aka “¹/₂+”, “50+%”, or erroneously “51%”) responsive nodes in the case where all nodes that communicate do so correctly and otherwise  ≤ (N - 1)/3 (aka “-¹/₃”) unresponsive and/or incorrect nodes, where N is the total number of nodes.[^Bracha]

---

‡ _{BFT always implies the asynchronous case, because otherwise BFT isn’t necessary.}

1.1 Byzantine Agreement

The proof is intuitive in the example scenario where every node is a voter and each candidate block is an election epoch. If every vote is correct, BFT only applies to faults which are unresponsive nodes; thus only a majority of votes is required because any ordering of blocks is always non-conflicting (or equivalently if the coordination of voting is synchronized such that conflicting order can’t exist, but then BFT isn’t applicable per the ^‡ footnote of prior section). For example, if validators of transactions never vote for a conflicting transaction such as a double-spend, then given two attempted elections for a pair of consecutive blocks of transactions, the minimum number of voters which commit to both elections is fₛ = 2T - N - 1, where T is the minimum quorum size for each election. Thus T ≥ (N + 1)/2 where 2T - N - 1 ≥ 0 because 0 safety is required given every vote is non-conflicting. But in the Byzantine agreement case wherein malevolent^* and/or asynchronous (forced by random propagation ordering) validators can vote for blocks that contain conflicting transactions, the minimum number of voters which commit to both elections fₛ = 2T - N - 1 must be greater than the number of excess voters not needed to form a quorum fₗ = N - T, so that a quorum for a conflicting pair of blocks can’t exist because there aren’t enough uncommitted voters to vote for it, i.e. T ≥ N - fₛ.[^Tendermint-safety]  Thus T ≥ (2N + 1)/3 where 2T - N - 1 ≥ N - T, fₛ is the safety margin, and fₗ is liveness.[^BFT-derivation] This result which is mathematically equivalent to N = 3f + 1 where f = fₛ = fₗ, is analogous to the N = 3m + 1 generals for m traitors result for the Byzantine Generals Problem (aka “BGP”).[^BGP]

Liveness in this context is the maximum number of unresponsive and/or malevolent nodes allowed for the system to not stall all quorums and/or censor for which blocks quorums are allowed. Safety margin is the minimum number of voters which must commit to a pair of blocks to prevent ambiguous ordering of blocks. Even if only a single election would ever be held for a set of signing keys which represent the voters,  Byzantine agreement applies in any nonsynchronous (aka “asynchronous”) case when there isn’t trust of a designated centralized tally, because voters can irrefutably claim that an epoch expired and they signed a new vote for a new epoch. It is even irrefutable that a trusted centralized tally did not receive a vote.[^he-said-she-said][^ambiguous-fault] Some systems may opt for more safety margin at the detriment of reduced liveness by choosing a larger minimum quorum size T.

Marbles in Jars Example

The proof in the case where nodes can be malevolent is easy to visualize with 3 colored marbles as voters: red, white, and blue. Given 3 jars representing ballot boxes for 3 elections, two marbles can be placed in each jar without any marble voting more than twice, i.e. no voter has cheated yet the result is ambiguous. Declaring any of the jars as the first epoch, results in two quorum choices (forks) for which jar is the next epoch. One jar has red and white, another red and blue, and another white and blue. This is why the proof requires that the excess of the quorum be less than ¹/₃ (aka “-¹/₃”). So by adding a green marble so that smallest minority reduces from ¹/₃ to ¹/₄ which is thus -¹/₃, the ambiguity is resolved because the green marble can only be placed in two of the three jars― again presuming no voter cheated to vote more than twice. Thus the +²/₃ instead of ¹/₂+ is required for quorums in the presence of possible malevolence given an asynchronous network, because the ordering of the quorums can’t be proven.

Note if any 3 of the 4 marbles are colluding, i.e. ²/₃ or more (aka “+²/₃”) of the voters are malevolent, they can vote for as many conflicting quorums (forks) as they wish and it will be ambiguous which of the 4 marbles is cheating, because given 3 sets of 3 jars, a different one of the 3 cheaters can vote in each set. And the honest marble has to vote on the fork which the quorum is extending, because otherwise not voting is indistinguishable from unresponsive. It can’t be irrefutably proven that the 3 malevolent marbles were cheating because they can each claim that other one became unresponsive when they each separately vote for one of the conflicting quorums; thus the justification that voting for more than two quorums became necessary. And the honest marble voted more than twice also or became unresponsive, so the 4 voters are all ambiguously malevolent from the perspective of any observer. And the honest marble voted more than twice also. Propagation order and responsiveness can’t be proven nor disproven in an asynchronous network.[^he-said-she-said][^ambiguous-fault]

---

* _{The adjectives “malevolent” or “attacking” applied to nodes means a colluding or centralized controlled group of nodes.}

I wrote a more easy to visualize explanation of the Byzantine agreement proof... can y'all understand this?

The proof in the case where nodes can be malevolent is easy to visualize with 3 colored marbles as voters: red, white, and blue. Given 3 jars representing ballot boxes for 3 elections, two marbles can be placed in each jar without any marble voting more than twice, i.e. no voter has cheated yet the result is ambiguous. Declaring any of the jars as the first epoch, results in two quorum choices (forks) for which jar is the next epoch. One jar has red and white, the next red and blue, and the last white and blue. This is why the proof requires that the excess of the quorum be less than ¹/₃ (aka “-¹/₃”). So by adding a green marble, the ambiguity is resolved because the green marble can only be placed in two of the three jars― again presuming no voter cheated to vote more than twice. Thus the +²/₃ instead of ¹/₂+ is required for quorums in the presence of possible malevolence given an  asynchronous network, because the ordering of the quorums can’t be proven.

Note if any 3 of the 4 marbles are colluding, i.e. ²/₃ or more (aka “+²/₃”) of the voters are malevolent, they can vote for as many conflicting quorums (forks) as they wish and it will be ambiguous which of the 4 marbles is cheating, because given 3 sets of 3 jars, a different one of the 3 cheaters can vote in each set. And the honest marble has to vote on the fork which the quorum is extending, because otherwise not voting is indistinguishable from unresponsive. It can’t be irrefutably proven that the 3 malevolent marbles were cheating because they can each claim that other one became unresponsive; thus voting for more than two quorums became necessary. And the honest marble voted more than twice also. Propagation order and responsiveness can’t be proven nor disproven in an asynchronous network.

https://github.com/cosmos/cosmos/issues/47   <--- they've gone silent because they realize they've wasted 3 years of work

After now understanding my invention better from an academic prior art perspective, I can now conclude that my whitepaper and invention will be more important Satoshi's. It is a fundamental innovation in the family of Byzantine fault tolerant systems. It solves the problems that Satohi's didn't. "He" was on the right track though.