It's a good idea to periodically replace old [[PGP]] encryption keys to minimize the amount of data exposed by cracking the old key. $ gpg --expert --edit-key F15F5BE8 … pub 1024D/F15F5BE8 created: 2008-08-09 expires: 2011-08-08 usage: SC trust: ultimate validity: ultimate sub 2048g/42407C74 created: 2008-08-09 expired: 2009-08-09 usage: E sub 2048g/4DA3FC0B created: 2009-07-26 expired: 2010-08-08 usage: E sub 1024D/EB357E60 created: 2009-07-26 expired: 2010-08-08 usage: S [ultimate] (1). William Trevor King [ultimate] (2) William Trevor King The usage characters are: * e = encrypt/decrypt * s = sign * c = certify (sign another key) * a = authenticate (e.g. log in to SSH with a PGP key) See `doc/DETAILS` in the [[GnuPG]] source directory for details on the output format (and the related colon listing format). If your primary key has expired, you can extend its expiration time with gpg> expire Note that my encryption keys have expired. This makes it hard for people to send me encrypted mail. Create a new encryption key with gpg> addkey Answering the prompts as you see fit (I usually pick Elgamal for encryption). You can also add signing keys with `addkey` (I usually pick RSA for signing, since DSA keys are limited to 1024 bits, see [ssh-keygen(1)][keygen]). There doesn't seem to be much to [differentiate Elgamml vs. RSA for encryption][diff]. With the `--expert` mode, you can select RSA (set your own capabilities) so that's what I do (since then I only need one subkey for all tasks). Several `gpg` operations require a particular subkey to be selected. Use `key` to select subkeys by index (marked with a `*`): gpg> key 1 pub 1024D/F15F5BE8 created: 2008-08-09 expires: 2012-05-24 usage: SC trust: ultimate validity: ultimate sub* 2048g/42407C74 created: 2008-08-09 expired: 2009-08-09 usage: E sub 2048g/4DA3FC0B created: 2009-07-26 expired: 2010-08-08 usage: E sub 1024D/EB357E60 created: 2009-07-26 expired: 2010-08-08 usage: S sub 2048g/3FB721E8 created: 2011-05-25 expires: 2012-05-24 usage: E sub 2048R/9CADC4D9 created: 2011-05-25 expires: 2012-05-24 usage: S [ultimate] (1). William Trevor King [ultimate] (2) William Trevor King If you get confused, there's also a `help` command. Save and quit when you're done: gpg> save Once you've got your key all fixed up, upload the new version to your chosen keyserver: $ gpg --send-keys F15F5BE8 You probably also want to post your new key somewhere on your website: $ gpg --export --armor -o ~/.gnupg/pubkey.txt F15F5BE8 $ scp ~/.gnupg/pubkey.txt you@somewhere:public_html/pubkey.txt Checking signatures ------------------- Here are some quick notes on checking signatures: $ gpg --check-sigs F15F5BE8 will list the status of signatures for which you have the signing key in your keyring. However, if you are missing one of the signing keys, you may get a message like 10 signatures not checked due to missing keys If you run $ gpg --list-sigs F15F5BE8 you'll see all the signatures, and you can use the usual `gpg --recv-key KEYID` to check out the ones you don't have. Adding user IDs --------------- If you get a new email account, you'll want to add it to your key. $ gpg --edit-key F15F5BE8 gpg> adduid … Optionally make the new ID your primary ID. gpg> uid 3 gpg> primary Finall, save your changes. gpg> save Don't worry about the `[unknown]` trust level next to your new ID. Once you've saved the key, it will change to `[ultimate]`. I imagine the initial `[unknown]` listing is because you haven't officially confirmed the new ID's signature by saving your changes. Inspecting GnuPG files ---------------------- If you want to see what's inside a GnuPG-generated file (e.g. you forgot which subkeys are in the ASCII-armored public key you published earlier), you can use: $ gpg --list-packets ~/.gnupg/pubkey.txt :public key packet: version 4, algo 17, created 1218318982, expires 0 … :public sub key packet: version 4, algo 16, created 1218319006, expires 0 … keyid: 7C572F3442407C74 … [keygen]: http://www.openbsd.org/cgi-bin/man.cgi?query=ssh-keygen&sektion=1 [diff]: http://www.samsimpson.com/static/pgpfaq#SubRSADH [[!tag tags/fun]] [[!tag tags/linux]]