Replying to Avatar Kruw

Cheaper for a single user, but not the average user. Impatient mixers subsidize patient mixers, but the overall cost is still higher for the group as a whole per anonset.

Can you elaborate what sort of scenarios that would benefit from restricting the pool size? Wasabi has standard amounts between 5000 sats and 1374.38953472 BTC all coinjoining in the same round. Fragmenting this into smaller pools would lead to less privacy, not more.
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Alfred Hodler 2y ago

I will concede that Wasabj may be a bit cheaper for impatient participants. However, Whirlpool is much cheaper the longer you mix. If you mix indefinitely, the price per anonset tends to zero. The Wasabi model never offers this.

As for your second assertion, having more pools doesn't lead to less privacy. Privacy is solely a function of anonymity sets, it has nothing to do with pool sizes.

Anyway, since I'm not affiliated with Whirlpool and I'm not on their payroll, you should ask them directly about some of their design decisions.

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Kruw 2y ago

The Wasabi model doesn't offer this sort of indefinite mixing because it doesn't make sense for one user to be charged for the blockspace a different user consumes.

On the second point, having more pools absolutely does lead to less privacy compared to combining all inputs in a single round because you eliminate all of the potential probabilities that are created from the composition of each additional input and decomposition of each additional output. Compare these two coinjoin transactions:

WabiSabi: https://mempool.space/tx/01a1a055719129397fb8344b5a09e6cfe72868c8e1d750e621d8b580c96bf77b

Whirlpool: https://mempool.space/tx/1825e9f7f0548fb4957d389b20e0e46d1ccc9ee50a75ebd19f7a49cdee761e50

In the WabiSabi coinjoin, there are 16 inputs for 0.001 and 13 outputs for 0.001 compared to 5 of each in the Whirlpool coinjoin. We can see the anonymity set is higher at face value due to the round's size, but the more important design choice is that there is not a 1:1 ratio of inputs to outputs of the same value. The 3 "missing" 0.001 outputs that are needed to complete our naive assumption don't exist since because they were either broken into smaller standard outputs, or merged into bigger standard outputs, inheriting privacy from all other inputs and outputs in the transaction that are not equal to 0.001 exactly.