The import/export key images command can be used to check the balance of a view only wallet.
But is there a way to use it to check the balance of an already set up Paperwallet?
Is it possible to get a transaction key image from a Paperwallet without exposing the spendkey or seed?
Is it possible to get a transaction key image from a Paperwallet without exposing the spendkey or seed?
It depends on your definition of "expose". Key images can of course be computed offline, even by some self-contained hypothetical device, but you are still "exposing" your spend key to that device.
You could do the necessary math on paper if you want, but you still expose your spend key to the paper. I do not recommend this method. :)
Christopher King has proposed an idea where the key image would be generated by a view key-derived output, but it needs some more review (and also involves substantial protocol changes).
It is also possible to compute some number of key images when you first generate the seed (it's "exposed" at that moment anyway) by using pre-chosen txkeys. However, there is currently no UI that implements such a thing (MyMonero is the easiest method of doing it manually).
Yes, it can be used.
In brief, you need to:
monero-wallet-cli.The trick is in doing 2. and 3. from a "cold" environment without ever exposing your private spend key to a network-connected device or having a chance of ever saving it somewhere. LiveCDs are ideal for this as they're read only. Only after you've wiped everything other than key images, you could plug in a flash-drive to be used to transfer them to the watch-wallet.
Here's a kind of guide for the process.
