Hi Antoine,

Consensus capture by miners isn't the only concern here. Consensus capture
by any subset of users whose interests diverge from the overall consensus
is equally damaging. The scenario I can imagine here is that the more light
clients outpace full nodes, the more the costs of security are being
externalized from the light clients onto the full nodes. In this situation,
it can make full nodes harder to run. If they are harder to run it will
price out some marginal set of full node operators, which causes a net new
increase in light clients (as the disaffected full nodes convert), AND a
redistribution of load onto a smaller surface area. This is a naturally
unstable process. It is safe to say that as node counts drop, the set of
node operators will increasingly represent economic actors with extreme
weight. The more this process unfolds, the more likely their interests will
diverge from the population at large, and also the more likely they can be
coerced into behavior they otherwise wouldn't. After all it is easier to
find agents who carry lots of economic weight. This is true independent of
their mining status, we should be just as wary of consensus capture by
exchanges or HNWI's as we are about miners.


On Wed, May 6, 2020 at 3:06 AM Antoine Riard <antoine.ri...@gmail.com>

> I do see the consensus capture argument by miners but in reality isn't
> this attack scenario have a lot of assumptions on topology an deployment ?
> For such attack to succeed you need miners nodes to be connected to
> clients to feed directly the invalid headers and if these ones are
> connected to headers/filters gateways, themselves doing full-nodes
> validation invalid chain is going to be sanitized out ?
> Sure now you trust these gateways, but if you have multiple connections to
> them and can guarantee they aren't run by the same entity, that maybe an
> acceptable security model, depending of staked amount and your
> expectations. I more concerned of having a lot of them and being
> diversified enough to avoid collusion between gateways/chain access
> providers/miners.
> But even if you light clients is directly connected to the backbone
> network and may be reached by miners you can implement fork anomalies
> detection and from then you may have multiples options:
> * halt the wallet, wait for human intervention
> * fallback connection to a trusted server, authoritative on your chain view
> * invalidity proofs?
> Now I agree you need a wide-enough, sane backbone network to build on top,
> and we should foster node adoption as much as we can.
> Le mar. 5 mai 2020 à 09:01, Luke Dashjr <l...@dashjr.org> a écrit :
>> On Tuesday 05 May 2020 10:17:37 Antoine Riard via bitcoin-dev wrote:
>> > Trust-minimization of Bitcoin security model has always relied first and
>> > above on running a full-node. This current paradigm may be shifted by LN
>> > where fast, affordable, confidential, censorship-resistant payment
>> services
>> > may attract a lot of adoption without users running a full-node.
>> No, it cannot be shifted. This would compromise Bitcoin itself, which for
>> security depends on the assumption that a supermajority of the economy is
>> verifying their incoming transactions using their own full node.
>> The past few years has seen severe regressions in this area, to the point
>> where Bitcoin's future seems quite bleak. Without serious improvements to
>> the
>> full node ratio, Bitcoin is likely to fail.
>> Therefore, all efforts to improve the "full node-less" experience are
>> harmful,
>> and should be actively avoided. BIP 157 improves privacy of fn-less
>> usage,
>> while providing no real benefits to full node users (compared to more
>> efficient protocols like Stratum/Electrum).
>> For this reason, myself and a few others oppose merging support for BIP
>> 157 in
>> Core.
>> > Assuming a user adoption path where a full-node is required to benefit
>> for
>> > LN may deprive a lot of users, especially those who are already denied a
>> > real financial infrastructure access.
>> If Bitcoin can't do it, then Bitcoin can't do it.
>> Bitcoin can't solve *any* problem if it becomes insecure itself.
>> Luke
>> P.S. See also
>> https://medium.com/@nicolasdorier/why-i-dont-celebrate-neutrino-206bafa5fda0
>> https://medium.com/@nicolasdorier/neutrino-is-dangerous-for-my-self-sovereignty-18fac5bcdc25
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