Re: [Taler] Synchronization and backup

[Jeff Burdges]

Do you have a use case for syncing that's not covered by the backup
scheme I proposed?  

It's not people without much money because my scheme actually permits
another device's reserve to be remotely shutdown and reacquired, albeit
with some delay. 

It's also not loosing money on the tablet that slipped into the couch
because again its reserve can be remotely shutdown.

On Fri, 2018-02-16 at 15:15 +0100, Florian Dold wrote:
> This is where we fundamentally disagree. Sync is user-friendly and
> useful in plenty of other products.

It's only used when products can freely duplicate the synced material
without consequence, not when the underlying semantics act like moves. 

> Let's hear other people's opinions and ask what non-technical people
> would expect.

What are you going to do about the guy who sees his balance disappear at
checkout?  

Or the person whose family member spends all their money? 

I'll point out that credit cards can be shared because debt has only
non-immediate consequences, not "you're sleeping on the street tonight"
or "this store appears to have robbed you".  Adoption will suffer when
Taler causes angry customers or even assaults on clerks.

Also, if we encourage sync then users cannot intuitively manage risk
associated with Taler balances like they manage cash.  A person can
easily imagine they should sync their phone with their work machine, but
their work machine might carry thousands, which a thief could quickly
spend if they get the phone and the wallet is not properly secured.

> My prediction is, if we implement only backups and no proper
> multi-device sync, somebody else will do it on top of our wallets,
> there will be two incompatible backup/sync systems and it will suck.

We must hide accidental syncing anyways for users who sync their home
directories somehow, probably by incorporating available device ids into
the wallet database.  We cannot actually remove coins belonging to
another wallet as some sync might propagate the removal, but we can
treat foreign coins as unspendable, although they should speed up
reclaiming the other wallet's reserve.  

Jeff

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