Post
Topic
Board Altcoin Discussion
Re: Is VCash the most scalable crypto around?
by
iamnotback
on 15/06/2016, 13:32:01 UTC

1. Since the chosen single node for each block is deterministic, then in theory it could be very vulnerable to botnet DDoS attack. More generally it lacks fault tolerance, which is critically needed in real world systems. A redesign to have simultaneous disjoint blocks from multiple delegates can't be allowed because there could be double-spends in the presumed disjoint blocks.

2. For DPOS, this is not decentralized control, because the minority has to accept the will of the majority on the election of delegate DPOS nodes, i.e. the permissionless attribute can be lost such as ChainAnchor being planned for ButtCON. No one can just standup a full node at-will. This also means there isn't really competition in terms of a free market rate for transaction fees.

Btw, Bitcoin-NG accomplishes basically the same deterministic node per block and with decentralized control over the selection of the delegate in real-time employing PoW, yet with chain reorganization issues.

3. The maximum speed (minimum delay) of confirmations is lower bounded by the slowest latency of block propagation to every DPOS node, because otherwise some nodes can't keep up. This can be reasonably fast say several seconds if you've got a very organized set of delegate nodes (but then you really don't have decentralized control), but this is not fast enough for some types of instant microtransactions.

4. Zero-confirmation double-spend transactions (aka Finney Attack) are even more plausible, because a colluding delegate node knows deterministically when it will win the block. Note block periods can be reasonably fast in DPOS, so 0-conf is probably not needed although not fast enough for some types of instant microtransactions, although such probably wouldn't be Finney attacked due to their small values.

5. Proof-of-stake is not a secure consensus algorithm, because for example the nothing-at-stake problem. We compiled a laundry list of flaws in proof-of-stake. Note I recently made a suggestion to jl777 and we mutually designed how to record check points for DPoS coins in a PoW block chain.



I am glad you are back youarenotback! Mostly I don't understand all you're saying, but at least your posts challenge me to try to learn new things. Thanx!

Let me try to unpack those points a bit for laymen:

1. Full nodes in DPOS are elected delegates. With Satoshi's PoW, we don't know which node will win the next block. So an attacker wouldn't know which node to jam with a DDoS attack. Any node attacked would simply not participate in competing to produce the next block, but this wouldn't harm the system at all. Whereas, when we designate the node that will decide what goes into the next block, then an attacker knows which node to attack. As well, a node knows when it will control the next block, and thus it can attack the network by withholding (although it would probably get voted out of being a delegate node soon, although it might be difficult to prove when it was a legitimate network hiccup or when it was intentional). I believe Bitcoin-NG may have an analogous weakness.

2. For me, this is the other huge weakness. With DPOS, the set of nodes which process blocks is static until the next voting. And even after voting, standing up a full node is not something an individual can choose to do by himself. There is always politics and centralization involved. The ideologically great thing about Satoshi's design is that anyone at any time can go standup a full node and process his/her transactions on any block he/she wins. The problems of course with Satoshi's design is that it doesn't scale and also that PoW economics of SHA256 means an individual can no longer win a block nor prevent the centralization of mining over time due to it being 100 to 1000X more profitable for the ASIC farms and because scaling can't work without centralization. So DPOS doesn't really gain anything that we can't get by centralizing Satoshi's design other than saving electricity.

I have another solution which I think is a better compromise than both of those. But I won't describe it, because surely others will start to figure out my design if I describe it further. I need to release it asap, so the discussion of its merits can be open sourced.

3. If one full node's block period is say 5 seconds, but the propagation to another of the full nodes is 10 seconds, that latter node will not be able to receive the new block from the former and produce another new block within its 5 second allocation. Thus the block period has a lower bound which is dictated by the slowest propagation on the network of full nodes. And 5 seconds confirmation is too slow for certain types of microtransactions. Imagine you want to start listening to a song, and you have it set to pay a microtransaction automatically, but you have to wait 5+ seconds everytime you want to click to listen to a new song you have not yet paid for. Or similarly when using microtransactions instead of a CAPTCHA. Even 1 second might be too slow! Vcash's Zerotime can't even get close to being fast enough. Probably Lightning Networks won't be fast enough either, not to mention it doesn't scale well.

5. DPOS (delegated proof-of-stake) is still POS with all its flaws. My desire is to attain Satoshi's security model, but with 100% decentralization, massive scaling, 1 second confirmed transactions, and no economic trend towards centralization!