Everybody is aware of the major problem with digital media: The retention time! The expected period can be critically reduced if the media (CD, hard-disk, tape, USB-key, flash, …) is not stored in safe environment (temperature, humidity, magnetic fields). Even if CD or DVD have a quite long retention time, other problems may arise in the future: new technology, media not readable anymore due to missing readers, who knows! Up to now, the best support remains paper and ink (of course if properly stored). It’s common to find old papers (>100 years old) still perfectly readable.
The problem of long period storage is particularly true with your private key(s). They are stored on your hard drives and you use them to sign or encrypt data. You backup then on.. other digital media! When about long period backups? Don’t forget that to revoke a key, you need your… private key! (personally, I still have very old keys (1996) that i can’t revoke as I lost them).
Then came Paperkey! This little tool has been developed to simply print out your keys on paper. Paperkey will certainly not replace your classic backup methods but will be some kind of last-hope-solution to restore a lost key.
WARNING: Any private key printed via Paperkey must be managed as your real key. Keep it in a safe place: A bank safe is a good place or hidden between the 2nd and 3rd tree at the end of your garden ;-)
Paperkey is really easy to use:
# cd $HOME/.gnupg # paperkey --secret-key secring.gpg --output my-key.txt
or, send the output directly to the printer:
# paperkey --secret-key my-secret-key.gpg | lpr
To increase the life time, you may of course print to special plastic paper or even engrave a piece of marble using your Dremel.
And how to rebuild your private key will you ask? Also using paperkey. You’ll need your public key but it’s not really a problem (all your contacts should still have it or via public key servers). Restore your key using the following syntax:
# cat <<END | paperkey --pubring=public-key.gpg >secring.gpg bla bla bla END
The software homepage is here. Now, you don’t have any excuse if you lost your private key…