Syncing labels, and other wallet meta data

[johnsBeharry]

Given I've use chaincase on phone A
And I get new phone B
When I install chain case
Then ...

Questions

• What kind of meta data need to be stored in the wallet?
• How can that meta data be synced / imported / exported?
• More generally, how is the user impacted in the above scenario if the labels are not able to be imported? Are there any cost benefits of having their labels in the new phone?

REF

• https://www.reddit.com/r/WasabiWallet/comments/eb1zzo/the_importance_of_good_labels/

[DanGould]

First, what are metadata?

In order to find all of one's bitcoin, in addition to their password I believe one needs at least the EncryptedSecret, ExtPubKey, AccountKeyPath and some gap limit between derivations that allows them to seek all of the derived addresses. This assumes key path identifies the network.

Beyond those that we can call "core" data are metadata. Metadata are used to improve user experience.

What kind of meta data need to be stored in the wallet?

Right now metadata stored Wallet.json comes down to Labels corresponding to PubKeys at a certain FullKeyPath and KeyState
these are used to identify where unspent bitcoin lives on chain, which key derivation has authority over them, and record how derived keys have been handled as far as who knows about them and whether or not they have been used or locked.

Native SegWit block filters and other chain state information like anonymity set could also be considered metadata, but differs in that it can be re-constructed at anytime with core data.

How can that meta data be synced / imported / exported?

Right now the local Wallet.Json file is not completely encrypted. It is a plaintext file. If all metadata were encrypted then perhaps we would be comfortable enabling users to take advantage of cloud storage of this data in-app. As long as no personally identifying data was attached e.g. if it were retrieved by hash Chaincase could in theory maintain these back ups. For now, when a user backs up their device this metadata is also backed up. That means metadata suffers from the same privacy issue as text messages or iMessage for iCloud backup. Encrypting the whole file would fix this. Right now the wallet file can be exported in the Wallet Info menu but not yet imported.

I've heard from at least one user that migrating devices from phone A to phone B app via backup is seamless because the wallet file comes right over with the app.

More generally, how is the user impacted in the above scenario if the labels are not able to be imported? Are there any cost benefits of having their labels in the new phone?

The greatest issue in losing labels in my opinion is losing track of which coins have sound privacy history but can't be marked as such. For example, if you sent a CoinJoined output from JoinMarket to your Chaincase wallet then using core data alone it would look like AnonymitySet = 1, the sender, but the sender is you and there is no good way to override yet. I suppose this is still a problem even with labels at the moment.

✨ In general it's more than nice to know where your coins came from. Contrasting coins attached to surveillance infrastructure with those from p2p can improve decisions that ultimately protect privacy.

[johnsBeharry]

Next line of questions would are

1. What data need to be synced between the wallet from config.json
2. Whats the data structure for both wallet.json and config.json ?
3. Is there a standard used by multiple wallets?
4. Are there any additional files dealing with user preferences that need a user may want synced?