While the other answers are correct, you don't need additional software. You can get all of this information from gpg if you add the
-vv command-line switch. (This means extra verbose.) For example, the easiest way to get detailed information about an OpenPGP-formatted message is to simply type:
And then paste the message into it (or pass a filename as an argument.) For example, pasting in the message above gives you the following detailed and interesting information:
gpg: armor: BEGIN PGP SIGNED MESSAGE
gpg: armor header: Hash: SHA1
:packet 63: length 19 - gpg control packet
gpg: armor: BEGIN PGP SIGNATURE
gpg: armor header: Version: GnuPG v1.4.13 (GNU/Linux)
:literal data packet:
mode t (74), created 0, name="",
raw data: unknown length
gpg: original file name=''
I vote YES on this important measure.
:signature packet: algo 17, keyid E48184B5B05676B1
version 4, created 1373178616, md5len 0, sigclass 0x01
digest algo 2, begin of digest 79 1e
hashed subpkt 2 len 4 (sig created 2013-07-07)
subpkt 16 len 8 (issuer key ID E48184B5B05676B1)
data: [159 bits]
data: [160 bits]
gpg: Signature made Sun 07 Jul 2013 12:30:16 AM MDT using DSA key ID B05676B1
gpg: using PGP trust model
gpg: key 92F88CF9: accepted as trusted key
gpg: key 6C77A726: accepted as trusted key
gpg: Good signature from "Alan Eliasen (http://futureboy.homeip.net/) <firstname.lastname@example.org>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 402C C0D3 D527 13E3 FB7C 7103 E481 84B5 B056 76B1
gpg: textmode signature, digest algorithm SHA1
In that output, you can see the 16-hex-digit key id clearly: E48184B5B05676B1
That will let you search for the signer in a keyserver using something like:
gpg --search-keys E48184B5B05676B1
By the way, I wrote the GPG guide that you reference, and I can assure you that I signed the above message. :)