Quote from: etotheipi on April 09, 2013, 07:08:27 PM

Quote from: Zomdifros on April 09, 2013, 06:58:27 PM

Quote from: etotheipi on April 09, 2013, 06:08:49 PM

-- Backup your wallet one time. Ever. Period. Forget about change addresses, it's all backed up with your paper backup. Print it or copy it by hand. A digital backup kinda works, but it is encrypted which doesn't help you if you forget your passphrase. You laugh, but this is by far the most common reason people lose coins -- not theft or hard drive loss. Plus digital backups get corrupted. There's no guarantee it will work when you need it 10 years from now.

Couldn't you just write your passphrase down and have an encrypted digital backup somewhere in your email or dropbox? That would solve the situation where your house burns down, just before you found out your parents lost the other paper backup you gave them.

Actually, this is a poor-man's Shamir's Secret Sharing scheme, and it's not a bad one, though you can only 2-of-2 out of it. Encrypt your backup with a really long passphrase on one sheet of paper. Write the passphrase on another sheet of paper. Now you need both to recover your wallet. But if you lose one, you're screwed.

Actually, you could encrypte multiple times, and get M-of-M out of it (3-of-3, 4-of-4, etc).

But the beauty of Shamir's Secret Sharing is that you can have, say, 3-of-5 backups -- print off 5 sheets of paper, and any subset of 3 is sufficient to recover your wallet. As I linked, it exists for Armory wallets, but only if you're comfortable with the command line. It will eventually be merged into the GUI... it's just going to take some work to unify all the backup options into an intuitive "Backup Center".

But the experience of this "electrician" is that, by far, the most vulnerable part of holding Bitcoins is losing your passphrase, your hard-drive, or online/virtual attacks (like the recent Skype malware). Not physical security. Most people are capable of physically securing a sheet of paper -- SSS will simply improve that.

Well that sounds reasonable indeed. The thing I'm most worried about by far are keyloggers and keeping the whole thing offline would pretty much solve that. I'm really looking forward toward the SSS solution within the GUI then, this would solve my other worry of somehow losing the piece of paper with the key.

One more question if you don't mind then: is there a risk that when you want to install Armory on your offline computer and transport it using a USB stick, malware somehow manages to copy itself on this stick and get onboard your offline computer, installs a keylogger and manages to get crucial information back on the internet using the same USB stick? Or is this way too far-fetched?