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# System prepended metadata

title: Privacy First Coin Selection

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# Privacy First Coin Selection


Ed Pratt May 6th at 1:47 PM
Looking for a bit of feedback on some designs for coin control in mobile wallets... For context, this wallet doesn't allow automatic coin selection to take place unless there are private coins within the wallet (anonset coins from prior CoinJoins). So no private coins = no automatic selection.
Problem: Cross contamination of coins being sent to different labels/recipients, exposing private information of previous transactions and labelled addresses
Solution: Letting users know that some sensitive information may be exposed to recipient
Is letting them know enough? How can we do this succinctly without over-explaining what's going on? (edited) 

![](https://i.imgur.com/lkhTghh.png)






14 replies

Christoph Ono  5 days ago
Is “Automatic coin selection” the right name for this feature, if it only considers “private coins”? With these specific UI options, how would I choose to send “non-private coins”, if I want to keep my “private coins” for later?

Christoph Ono  5 days ago
In the first screen, I don’t see an option to access the coin list. How do I get there?

Christoph Ono  5 days ago
Something like this maybe.

![](https://i.imgur.com/Kp54uns.png)



Ed Pratt  5 days ago
The standard setting in this application is to automatically select coins on behalf of users when making payments (the algorithm used is essentially Branch & Bound - minimising change outputs). However, users can turn off this standard setting and opt for manual coin selection. Hence the Toggle.
However, the issue with this is that the application still opts for automatic selection even when it can't perform this task. This happens when users don't have any private coins available for selection. So, they have to disable the feature and manually select coins.

Ed Pratt  5 days ago
I like some of those suggestions you've put above, thank you! I'll have a play around with these and see which solution works best :i_love_you_hand_sign:

Ed Pratt  5 days ago
Also, do you think even if coins are automatically selected, you'd still like to see a list of which ones are chosen?

Christoph Ono  5 days ago
I get it. And I think the name of the feature is incorrect.

Christoph Ono  5 days ago
Probably depends on the user. For transparency, might be good to have. The point of having picky auto-selection is to not have to worry about it, so I would’t expect most people to check.

Ed Pratt  5 days ago
Right ok, think I misunderstood you before. I think you're right regarding the naming of this feature... due to the complex nature of the privacy first I think the solution you opted for could also help solve that pain point :slightly_smiling_face: Thanks for you help! Might bring it up at the next jam/review!

[](https://i.imgur.com/G5k137p.png)


:raised_hands:
1


Ed Pratt  5 days ago
Needs a lot of UI work, but concept is getting there...

Christoph Ono  4 days ago
Looks great. A cool feature would be to auto-mix. So if you don’t have enough anonymized bitcoin, the wallet will just do it for you and then send your main transaction. There would have to be an estimate on time and cost though, which I am sure is just super easy to do.

Christoph Ono  4 days ago
Taking one step back, a user might want to just set a certain amount of bitcoin aside in a separate “private wallet”. Maybe I could say that I always want to have €500 in “private coins” and the wallet automatically makes that happen (when fees are low). That way I don’t always have this problematic choice in the moment of transacting.

Ed Pratt  1 day ago
Those are both great ideas, lots of interesting stuff to be played with. The alternative would be some sort of pre-signed coinjoin on a daily/weekly/monthly basis that makes sure users coins are private

Johns Beharry  < 1 minute ago
We should also post this thread to github discussions cause soon its going to disappear forever and I think this one is really valuable to keep.