Topic: Interleaved Mining - Increase decentralization of full nodes and mining - page 2. (Read 3636 times)

This is incorrect for several reasons.

1) The scenario you described is only valid for the POS block being currently mined, however this is no different than POW miners attempting to mine blocks and come up with 2 blocks around the same time. The network will eventually go with one fork and the other will be orphaned. In this case, it is the POW miners who decide which POS block is built atop.

2) Yes, you are right that pure POS is insecure because of the grinding problem which pretty much every POS coin tries to resolve via checkpointing by trusted parties.
In Interleaved mining, the checkpointing is instead done by POW miners based on whoever mines the next POW block just as the correct chain history is decided by POW today, POW will decide which POS block is the preceeding block.

To simplify this, think of POS blocks no different than ordinary Bitcoin txns, POW miners decide which is valid and in what order.

3) While i have not described the POS algo in detail yet (wish to get the high level idea across first), my current thinking wrt the "strength" of a POS block would be a combination of coins * age where inclusion of a POS block will consume coin age, thereby greatly reducing the probability that the same party will mine another POS block in the near future.

This reduces the security model of the entire chain to that of POS. Any attacker can just wait for a POS block, then use his stake to perform a double spend by minting a block and just keep doing that forever at zero cost every other block.

That is actually an interesting idea. The downside would be that it would effectively be a blocksize decrease as older nodes won't see POS blocks, only to see the relevant txns 20min later in the next POW block.

My personal opinion on the softfork idea is that if we are going increase blocksize sometime in the future, we would need a hardfork anyway. Increasing the blocksize has centralising effects and implementing this proposal together would do much to counteract and even improve decentralisation considerably.


Yes, this has been brought up, although id like to hear from a miner why this might be an issue if all miners are affected equally by this.

I think that would be speculation on your part.

Bitcoin by design was intended to reward you according to your contribution.
Having a larger share of mining should not result in more rewards than your respective hashpower.
However, the Selfish Mining paper has proved that this is not the case in practice and this proposal is an attempt to fix this.

Considering that all the large miners and pools which have 90% of the hashrate are public today, it will be very hard for them to publicly decline a change which improves decentralisation without a valid reason.
Also, this proposal keeps all inflation rewards with POW miners, POS miners are introduced merely to incentivise full nodes and resolve block propagation issues with a very small block, which will not affect revenue of POW miners in any noticable way.

Your economic assumptions regarding POS are incorrect:

http://www.truthcoin.info/blog/pow-cheapest/

You could do it via soft-fork.  You just need to add a rule that the transactions for the first 50% of the block has a POS proof.

POS N:  validated by POS




POW N+1:




POS N+1:  validated by POS




POW N+1:




You would need to add a modification to the protocol to propagate the POS proofs, but that isn't a massive deal.

Non-upgraded clients would just track the POW blocks, but each POW block would need a POS block proof to be accepted by other miners.

One characteristic of this system is that hashing power is useless between the time a POW block is found and the next POS block is found. 

Yes I did and clearly understood that you are trying to change the mining protocol that requires a hard fork. This protocol change will push towards decentralization of mining. But, the existing super powers of mining world does not want that. So, they'll continue to mine their favorable longest chain and thereby your hard fork will lose out.

p.s. If you still dont understand, then read my post again.

Did you even read the post?

A hard fork that does not incentivize existing bitcoin miners wont ever survive. You'll always end up creating an Alt coin.

Interleaved Mining

Proof of Work
Pros:

• Battle tested with largest market cap coin, is secure and works
• Requires an expense of resources external to the coin economy, ensuring that miners can only choose to extend one path on the chain at any point of time
• With the growing role of decentralised electricity generation via Solar/Wind, has potential to be more decentralised in future
• Miners have serious skin in the game (huge capital investment in hardware, cooling, location, etc..) with potentially low margins. It is in their interest to think long term to be able to recoup their investment.

Cons:

• Extremely wasteful compared to a centralised solution (aka SQL database)
• Environmental concern with energy burned
• Advent of Pooled mining has caused excessive centralisation
• Large solo miners further threaten decentralisation
• Maturation of industry has resulted in relatively large barriers to entry (mining hardware purchase, sourcing of cheap electricity)

Proof of Stake
Pros:

• Far cheaper than POW
• Low barrier to entry - Allows anyone with coins and running a fullnode to participate
• Pooled mining not possible without custodial risk?
• More decentralised because it incentivises currency hodlers to run a full node for mining rewards

Cons:

• Insecure - All solutions thus far require some form of centralisation (authority/checkpoints) or trust, something which is unacceptable for Bitcoin.
• Nothing at stake problem allows large stakeholder miners to mine all possible forks, eventually find a fork where they come out on top, allowing them to rewrite history at point in future.
• Not suitable for coin distribution as the first recipient of coins can always rewrite the entire history at any point in the future due to the fact that he owned 100% stake at one point of time.
• Unlike POW, cannot objectively determine best/longest chain as there is no real cost to produce a larger chain(Nothing at stake). Resulting in checkpointing by trusted parties

Interleaved mining  
By combining both mining methods, we can resolve or diminish many of the cons of both methods, while retaining all of their benefits.

  The idea is simple, to alternate the mining algorithm between POW and POS every block (ie POW for all odd blocks and POS for all even blocks). POW blocks will retain all inflation subsidies to uphold the social contract promised by the original protocol. Transaction fees will be retained by the respective miners of the blocks, as is the case today. Since POS blocks will not receive new coins, the POW block reward will be doubled to stick to the original coin distribution schedule.

Block intervals will remain at 10 minutes.

To resolve block propagation delays causing POW miner centralisation, POS blocks will have a smaller block size limit to allow smaller miners to compete more equitably. This block size should be low to ensure that smaller POW miners are able to download and validate the block as quickly as possible such that orphan risk is extremely low. On the other hand, POW blocks may be considerably larger as POS miners are much less affected by propagation delays.

https://i.imgur.com/MHV490q.png

The addition of POS blocks in between POW blocks has many advantages, chiefly that having 51% of mining hashpower is no longer sufficient to control the network. For example, even if a miner had 51% of hashing power, he will not have 51% of stake(combination of coin age and coin quantity) to produce a valid POS block, allowing the rest of the network to produce a valid POS block and continue building atop the chain.

The key advantage is that by adding another dimension to mining, we make it much harder for anyone to control 51% of block generation beyond a single block.

Introducing POS blocks will greatly incentivise the running of full nodes and increase the decentralisation of validation of the chain.

In pure POS mining, it is possible for a POS miner to in future come up with a longer valid chain, however with interleaved mining, this is not practically possible as the next POW block will quickly seal the chain with proof of work, thereby rendering the attack unviable.

Motivation
The goal of introducing POS blocks is not for POS’s sake, rather it is to increase decentralisation of mining and fullnodes by allowing smaller alternate blocks (POS blocks) to incentivise running of full nodes which at the same time allow rapid propagation of the blocks to POW miners, thereby preventing implicit selfish mining attacks caused by propagation delays.


Benefits

• Solves 51% attack problem by adding another dimension of miners (POS)
• Incentivises full nodes via POS mining, thus increasing decentralisation
• Maintains Status Quo for POW miners by keeping inflation subsidy rewards solely for POW miners
• Halves the running cost for POW miners while keeping revenue almost the same, potentially doubling profits for POW miners in the short term.
• Hardens the Bitcoin blockchain by adding 2 dimensions of mining
• Nothing at stake problem is solved by interleaving POS blocks with POW blocks, preventing a rewrite of history by any large holder. Any attack on POS or POW for that matter, only has a 1 block window, before the alternate mining method takes over.
• POS Grinding attack is not possible as POW blocks serve as objective checkpoints
• Solves large block propagation problem by keeping POS blocks smaller to ensure fast propagation to POW miners, allowing smaller miners to compete more equitably, thereby allowing larger blocks

Cons
Requires a hardfork