PGP GPG Web of Trust, Find Most Secure Path

Web of Trust explaination

http://zarb.org/~gc/html/pgppathfinder.html  (http://pgp.cs.uu.nl/)

Showing trust levels with "gpg":
gpg --with-colons --list-keys
The second field and the ninth field are the ones you want. The
second field contains the validity, and the ninth field contains the
trust setting. See doc/DETAILS from the GnuPG distribution for all
the possible values there.
2. Field: A letter describing the calculated trust. This is a single
letter, but be prepared that additional information may follow
in some future versions. (not used for secret keys)
o = Unknown (this key is new to the system)
i = The key is invalid (e.g. due to a missing self-signature)
d = The key has been disabled
(deprecated - use the 'D' in field 12 instead)
r = The key has been revoked
e = The key has expired
- = Unknown trust (i.e. no value assigned)
q = Undefined trust
'-' and 'q' may safely be treated as the same
value for most purposes
n = Don't trust this key at all
m = There is marginal trust in this key
f = The key is fully trusted
u = The key is ultimately trusted. This often means
that the secret key is available, but any key may
be marked as ultimately trusted.
9. Field: Ownertrust (primary public keys only)
This is a single letter, but be prepared that additional
information may follow in some future versions.

$ gpg --with-colons --list-keys
tru::1:1304353633:1309537403:3:1:5
pub:-:4096:1:EEB79C73B8EC3AC9:2009-05-18:::-:Geoffrey Thomas ::escESC:
pub:e:2048:1:B576D161BD18CA24:2010-04-27:2010-08-25::-:MIT 6.033 sp2010 (Key for hands-on #6 - Crypto) <6.033-staff@mit.edu>::sc:
sub:e:2048:1:6AC6D22E0D016CE7:2010-04-27:2010-08-25:::::e:
pub:-:1024:17:882E0BAD0B72EB0F:2009-04-27:2012-01-20::-:Barack Hussein Obama (DOD) ::scaSCA:
pub:-:4096:1:4372CDFF95630310:2010-04-08:::-:Chris Post ::scESC:
uid:-::::2010-04-09::A5898B3ADF21B9261C6F342945D94F0392F4E1F8::Chris Post :
sub:-:4096:1:365783180773FB2D:2010-04-08::::::e:
pub:u:2048:1:304085A3F33AAB16:2011-05-02:2011-07-01::u:HaoQi Li ::scESC:
sub:u:2048:1:182358B0146708AD:2011-05-02:2011-07-01:::::e:

leaf of trust graphs

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GPG tutorial