Quote from: ben-abuya on June 22, 2011, 11:49:08 AM

How would proactive sharing work in the context of bitcoin? Who decides that shares are renewed? It will be interesting to see if there are established open source tools that give us threshold, proactive sharing and verifiability.

I am trying to work that out right now.

The idea is, that the account holder also has access to a majority of devices holding the shares. So, the account holder would press the "redistribute secret" button on all the devices he has access to, and the devices would generate and distribute new shares using a suitable protocol. Those devices which are not present at that moment, would not get their new share, and their old share would, from that moment on, be useless.

It is probably easier (but less secure) to have a single trusted device redistribute the secret.

To my knowledge there are no open source tools which do that. So it would be a matter of implementing and having it subjected to peer and community reviewing. The good part is, that it does not affect Bitcoin at all and would be a seperate piece of software, using the RPC API of bitcoin.

Quote from: ben-abuya on June 22, 2011, 11:49:08 AM

I understand that Bitcoin already supports an m of n scheme for signatures. Any individual key can easily be verified in the usual way and a renewal can be accomplished by getting keys together and transferring to a new address with new keys.

Is this multiple signature feature for m of n or is it rather for 2 of 2. What I saw in the code was rather a 2 of 2 kind of scheme - and I did nto check if it is really turned on or just in the code but disabled.

Getting the coins to a new address with keys is certainly possible and fun for the freak, for the John Doe user it is a no-go. Just compare: This new fine leather wallet is secure. You just have to move your coins into a different one every other day!

Quote from: ben-abuya on June 22, 2011, 11:49:08 AM

I don't know if pluggable pc's are the best solution. I wouldn't want the keys being read on any machine that was connected to the net. I think the best safe solution is to create an unsigned transaction on your regular computer, write it to a usb drive, sign it on a secure device that has no connectivity but can show the amount sent and address sent to, and then send it via the regular computer. The secure device would also not have any persistent storage. Keys would be stored on additional usb drives.

I agreed with that until yesterday.

Imagine you lose the secure device. Or drop it. Or your cat pees on it. Your son runs his bike over it. There goes the access to all your bitcoins. Embarrassed