Replying to kpr797

But shouldn't it be statisticallly impossible to determine if its a decoy or not, if decoys are selected in an intelligent manner (ie. in a random distribution)?
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Hanshan 7mo ago

thats basically correct

but theres nuance, as always.

Because we know the age of outputswWe don't want a *completely random distribution* we want a distribution that matches the age distribution of *how people actually spend*

But we don't know how people actually spend because everything is obfuscated

What we can do is guess and do statistical analysis on how we *think people spend and compare that to what actually appears on chain

As I recall STN's Monero tracing tool (which doesn't actually trace Monero 🙄) heuristically identifies old outputs as the likely spend because the generally used decoy selection algo is biased towards recent outputs, making old output stick out.

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kpr797 7mo ago

That sounds like a glaring issue. Are heuristics like that any good?

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Hanshan 7mo ago

nobody knows, which is kind of the point.

pretty much every agrees that older outputs are more likely to be cold storage or lost coins or whatever.

but nobody knows *how much more likely*

theres considerable debate if it's even knowable at all.

so for now, its just comparing a guess about what someone thinks the real age distribution of spends should be

against the age distribution that appears.

decoy selection is hard and this has always been a problem. which is why Monero will move to full chain membership proofs and dump ring signatures altogether.