Quote from: Forp on June 22, 2011, 04:16:17 PM

Thank you for pointing this out. I checked this in the code. With the exception of script.cpp and script.h it is not used. Especially, it si not part of the GUI.

Guess we should make it available ASAP.

Still it is only part of the solution. It increases the risc of loss. Now you should not lose TWO things. Before that, you whould not lose ONE thing.

Well script.cpp is the core. It's completely integrated into bitcoin, it's just not in the default GUI. Before putting it into the GUI I'd add support to the RPC. I don't understand why this increases the risk of loss. If you only need 2 out of 5 keys, you can lose three of them and still be able to access your account. You can even do 1 out of 5 if you're worried about that and less worried about theft.

Quote from: Forp on June 22, 2011, 04:16:17 PM

Ok. Then replace "secure device" in my sentence by "usb drives/smartcards/whatever".

There is a thing which holds your key. This thing gets broken - you lose your money. You copy this thing - you increase your risc of having it stolen and you have to redo the copy every time you generate new keys.

The solution I am contemplating takes care of BOTH aspects.

You cannot be compromised so easily, because you need more than one device to access your money.

You do not increase your risk of loss, because you "things" are replaceable.

With the suggest form of secret sharing you get both advantages for one price. Grin

Well there's always a tradeoff between loss and theft. If you're worried about loss but not theft you'd want 1 out of n where n is big. If you're worried about theft and not loss you'd want n out of n. You're usually worried about both so you compromise and choose m out of n somewhere in the middle.

I think a complimentary technique is to use a dead man's switch, so that in the case of loss Bitcoin will transfer your funds to another account after say 30 days. This is also already built into bitcoin scripting. That way you can focus less on loss and more about theft in your crypto protocol.