Order utxos by age about coinselect HOT 4 CLOSED

Hm, I wrote this issue because that's how trezor web wallet currently selects coin, but thinking about it more, I am not sure what is the correct ordering.

There is a paper from late 2016 "Simulation-based Evaluation of Coin Selection Strategies", it seems the best utxo selection algorithm for low fees is from AndroidWallet, which sorts utxos by priority - that is, value * inputAge

This selection algorithm however results in the biggest utxo set.

The FIFO algorithm (that is, the same one that trezor wallet has right now) has only slightly higher fees and lower utxo set; however, it reveals the oldest user's utxo in every transaction (privacy concern).

I cannot decide at this moment :D (I just know I don't want to solve a knapsack problem here like Core does.)

We can provide all the strategies and leave it to the user to select, but I don't like that, I think the default should be sane.

from coinselect.

@Runn1ng this could easily be added to the default sorting function.

But any advanced heuristics may need to balance privacy and eventual fees in this equation.

from coinselect.

I don't think age is as important with priority policy dropped in most clients.
Close?

from coinselect.

yep

from coinselect.