It appears I reinvented a bitcoin wheel:
https://bitcointalk.org/index.php?topic=104086.0I mean, it's a "standard" crypto trick, but it also looks like Vitalek created exactly the same thing 6 months. And I probably could've used his code. My solution uses a stupidly-inefficient version of matrix-inverse, but that's because it was ridiculously compact, and I thought 8-of-N would be overkill, anyway. He says his could support up to 15-of-N and wanted to go up to 255-of-N. Meh...
That is the plan, correct, to have a QR code for each split paper backup that could scanned in easily?
With this feature you could keep a brain wallet by memorizing a passphrase but also backup the generated private key by splitting it N-ways among family, attorney, etc., in case of death, and put recombination instructions (and may one of the split QR codes) in your will.
Yes, there will be QR codes everywhere. But I don't have plans to implement a QR reader in Armory unless someone basically does it for me... it's annoying to type in paper-backup stuff, but it should be a once-every-3-years kinda thing for most users.
I like the idea of putting one in your will (that's essentially giving it to an attorney, though, isn't it?). You could also have fun nesting these, if you weren't afraid of mind-blowing complexity -- split the secret into M-of-N, and then fragment some of the pieces further. It would allow you to create asymmetrically-important fragments, so that each piece really just represents some fraction of the secret, some pieces worth more than others.
I guess you'd get the same thing from simply producing 100-of-N fragmenting, and distributing multiple pieces to each person/place. Then you can keep 10% in your bookshelf, 30% in a safe-deposit box, etc. That would be a ton of data, and QR codes probably wouldn't be very convenient either. This really isn't all that useful, just kinda fun to think about ... It's late, maybe I should sleep instead...