On 09/24/12 16:59, Andy Lutomirski wrote: > I don't really trust CDs or USB keys as a long-term storage medium,
This is why I made Tarsnap keys printable -- of course, printers bring some security concerns and paper has its own durability issues too. > and tarsnap keys are kind of long (~5kB). So here's a feature > request: let me upload a possibly encrypted key file to tarsnap.com so > I can re-download it if necessary, presumably using only my account > password to authenticate. This is something I've wondered about doing for a while; I'd prefer that people not use such a feature, but I can certainly imagine it making life easier for some people. > To clarify, here's a concrete proposal: > > $ tarsnap-upload-key keyfile.key > > This will generate a random 128-bit key, encrypt the key file against > that key, and send the result to tarsnap.com (i.e. somewhere in > AWS-land). It will then display that key in some nice form (base64 > with no I, l, or 1, for example), so I can print a few copies on > paper. Then I can stick those pieces of paper somewhere safe. Is having that utility generate a decryption key for you better than just using the (already existing) functionality for passphrase-protected key files? (One obvious advantage is that there's no way for someone to pick a poor passphrase if an encryption key is generated by the utility, I suppose.) My idea was that if I did this I wouldn't add any extra encryption but have the utility refuse to upload a key file which wasn't passphrased. > There are plenty of elaborations possible. For example, tarsnap.com > could refuse to let me download the encrypted key unless I can prove I > know the key-wrapping key (e.g. by presenting some hash of the key, > where that hash is stored along with the key). There could also be a > tool that implements basic secret-sharing on the wrapping key, so I > could require, say, 2 out of 5 pieces of paper to recover the key. > > Thoughts? This requires some server-side help to work. This is certainly something which I could add (and as I mentioned above have thought about before). I'd be interested in hearing from anyone else on the list who would like to see this functionality. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
