Nick Szabo  🔑

But there is nothing invalid about a chain that has been re-orged, miners will be economically incentivised to mine on the longest (re-orged) chain.

Right, knowing about a 51% attack doesn’t change anything. Miners are not required by consensus rules to build on the blocks of other miners.

I am not sure what you are trying to say here but miners are incentivised to mine on the longest (valid chain) to decrease the likelyhood of their blocks being orphaned

Assuming that incentives will make people do the right thing is still an assumption. Without full nodes to hold minors accountable that incentive goes away.

Agreed. I am talking about what security diffs a full node vs an SPV node has for an individual actor, not under the assumption that everyone runs SPV. The valid chain is the chain with the most difficulty that still complies with protocol rules.

And an SPV wallet cannot know the rules have been satisfied and therefore cannot know if it is following the chain at all.

Agreed. I am not at all arguing that spv clients can determine whether or not blocks are following the inflation shedule. I am arguing that under the conditions necessary for a miner to inflate the supply like that, a re-org attack can be also done which affects both node types.

The inflation example is silly, if somebody introduced an inflation fork it would very soon be common knowledge and SPV clients could be patched in updates or configured by their users to point to full nodes that run their desired fork.

It's also important if you're accepting payments to know about 51% attacks so you can quickly suspend confirmations until the attack ends. Right?

Hmm. How can a miner know any more than an spv node is a 51% attack is occurring? Doesn't make sense