MWixnet and possible miner centralization risk

I was working through the math of MWixnet with payjoins and coinswaps and am excited about what the future holds for MW/grin. I do have a concern to discuss regarding a possible mining centralization pressure this could produce.

Before mining centralization… a discussion about some user-side MWixnet centralization pressures:

  • Mix Quantity
  • Mix Reliability
  • Security
  • Price/Speed

Mix Quantity: This one is obvious but the MWixnet benefit is maximized as the number of included transactions is maximized. It therefore seems that users will gravitate to whichever MWixnet is producing reliable high transaction count outputs. This is a self-reinforcing loop and may be hard to combat (assuming a reason is presented that it needs to be combated).

Mix Reliability: As I understand it, MWixnet requires all the nodes be defined at the start. All nodes must be online at the time of mix. Failure of one Mixnode brings the entire mix down. It is not clear to me yet how users are to decide on a start, middle set, and end Mix Node, but somehow I suspect a reliable DOS proof set of nodes will become known to the community and the risk of using any other set would include a risk of a failed MWixnet (which is admittedly not catastrophic but could cost the user a day before mixing). I think human nature is to keep using what works and this will therefore increase centralization.

Security: For MWixnet to work as intended, one of the nodes needs to be honest. I could envision several ways that a particular MWixnet would start to build trust within the community but when such node sets start to develop it could be hard to startup a new WMixnet from scratch and get any level of transaction volume. This adds to the centralization pressure.

Price/speed If a particular MWixnet started to have 1000+ transactions a day/half day/hour…, it could lower its price. When it starts to fill up there isn’t really a pressure to find new reliable nodes, because the net can always just start to publish more frequently. Quicker maxed out mixing is actually a further benefit in some cases so this is even further enforcing. Cheaper/faster is actually a good thing for the user (provided its not so cheap there is a spam/bloat attack) but would be another source of centralization pressure.

None of the above is really a problem, it’s just economics. However, it does seem to provide some potential for miner-side centralization pressure which would be bad.

Miner-side centralization pressure?
High fee block: There is already a reality that pools tend to consolidate and get big and grin mining pools are no different. Given the 1 minute block time of grin, there is pretty reasonable assumption that a sufficiently large pool would mine a block within any given 10 min window. This is already true of a big pool like 2miners.com. Given that MWixnet is, by definition, not time critical, it seems reasonable that a WMixnet associated with such a pool could hold onto the high fee/1000+transaction block (not transmit it to other nodes) such that it would be sure to include it in whichever block it mined close to the associated time. This is particularly true if they start filling up a block such that they publish more than once a day. Who is to know (or care) that they waited 10 extra minutes to control the block. Statistic would start to show that the associated pool was more profitable and, history shows, miners would flock to the pool. No privitization harm done… except the blockchain becomes more centralized. While user centralization in MWixnet’s might not be bad, miner centralization is recognized to be bad.

Truthfully, mining pools running trustworthy WMixnodes is not so far-fetched. Miners have incentive to keep a network healthy and pools likely have servers/infrastructure most ready to resist DOS attacks (and thus reliable mixes). It seems reasonable future trusted WMixnets could include pool operated WMixnodes as trustworthy.

Conclusion
Anyway, I am not saying the sky is falling but I wonder what people think about this. Am I wrong to suggest that the final WMixnet could control who knew about their valuable block (that would be great and a little embarrassing)? Certainty hording fees is not a new problem for blockchains so maybe it is already solved. However, normally non-private chain users just broadcast their transactions into the system so the difference here is that WMixnet incentivises the users to give a particular node some control of timing. Is this a valid concern?

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MWixnet will make from Grin big mixer.
Government’s will ban mixing nodes and miner’s pools. MWixnet it’s a bad idea for miners for Grin and for griners we will loose this war.
Frank Richard Ahlgren III, a Texas resident, was sentenced to two years in prison and ordered to pay $1,095,031 in restitution for tax crimes in the sale of $4 million worth of Bitcoin. This is the first purely cryptocurrency-related tax fraud case in the United States. Ahlgren moved Bitcoin through multiple wallets, conducted face-to-face peer-to-peer transactions, and used mixers such as CoinJoin and Wasabi Wallet to hide the flow of funds. — link

@GrinDarkNetBank The information you are posting about someone conducting tax fraud has literally nothing to do with grin. Privacy is great, but if you try to use privacy projects for criminal activities, the law will judge you because of the activities being criminal. Technology is neutral, what you do, the actions you take, that is what you are accountable for.

No, it has nothing to do with miners. In a dystopian fantasy with overstepping regulators, you could argue nodes that run MWixnet nodes in some countries could get legal issues since they can be argued to facilitate mixing and earning from it (a very small amount).
However, no single node is responsible or facilitating as such, and as mix node you can in theory just send your funds to anyone/charity/void, and you would not be earning from it and therefore not be liable to any charges.

Not interesting at all and not the first. There have been many cases were people use crypto for tax fraud. Again, if you do something criminal, that is on you. Or should we ban dollars since they are favorite with many criminals, or ban plains because they can be flown into towers.

Grin not confidential then don’t do from it mixer coin fully confidential instrument for criminals.

Sorry, you messages is a bit hard to understand, can you do a language checks before posting :pray:
Indeed, Grin is not confidential, but there are no addresses, no amounts, only output link-ability can be seen. MWixnet will make linking output much harder. IMO more important even is default PayJoins which are coming to Grin. With PayJoins, there is no way to tell the direction of a transaction and there is no need for special mixing nodes, its all peer to peer. So it is a very nice step up in privacy for regular transactions. Will grin be the most private coin?.. hell no! ,Grin has great privacy preservation by default, at basically no cost since its true focus is minimalism and scalability.
Criminals will and should always chose privacy projects like Zcash and Monero over Grin which is a great thing.

Criminals are using fiat currencies, but they are not confidential, with CBDC they will be more restricted, cause real criminals are central banksters, Grin as money is neutral for any activity, criminal or not, extra features can be built on top, Mwixnet is good example, next big thing is p2pool to avoid mining centralization.

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