Distributing keys

Distributing keys
The GNU Privacy Handbook
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Chapter 3. Key Management
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Distributing keys
Ideally, you distribute your key by personally giving it to your
correspondents.
In practice, however, keys are often distributed by email or some
other electronic communication medium.
Distribution by email is good practice when you have only a few
correspondents, and even if you have many correspondents, you can use
an alternative means such as posting your public key on your World Wide
Web homepage.
This is unacceptable, however, if people who need your public key do
not know where to find it on the Web.
To solve this problem public key servers are used to collect
and distribute public keys.
A public key received by the server is either added to the server's
database or merged with the existing key if already present.
When a key request comes to the server, the server consults its
database and returns the requested public key if found.
A keyserver is also valuable when many people are frequently signing other
people's keys.
Without a keyserver, when Blake sign's Alice's key then Blake would send
Alice a copy of her public key signed by him so that Alice could
add the updated key to her ring as well as distribute it to all of her
correspondents.
Going through this effort fulfills Alice's and Blake's responsibility
to the community at large in building tight webs of trust and thus
improving the security of PGP.
It is nevertheless a nuisance if key signing is frequent.
Using a keyserver makes the process somewhat easier.
When Blake signs Alice's key he sends the signed key to the key server.
The key server adds Blake's signature to its copy of Alice's key.
Individuals interested in updating their copy of Alice's key then consult
the keyserver on their own initiative to retrieve the updated key.
Alice need never be involved with distribution and can retrieve signatures
on her key simply by querying a keyserver.
One or more keys may be sent to a keyserver using the command-line
option
--send-keys
The option takes one or more key specifiers and sends the specified
keys to the key server.
The key server to which to send the keys is specified with the
command-line option
--keyserver
Similarly, the option
--recv-keys
is used
to retrieve keys from a keyserver, but the option
--recv-keys
requires a key ID be used to specify the key.
In the following example Alice updates her public key with new signatures
from the keyserver
certserver.pgp.com
and then
sends her copy of Blake's public key to the same keyserver to contribute
any new signatures she may have added.
alice%
gpg --keyserver certserver.pgp.com --recv-key 0xBB7576AC
gpg: requesting key BB7576AC from certserver.pgp.com ...
gpg: key BB7576AC: 1 new signature

gpg: Total number processed: 1
gpg: new signatures: 1
alice%
gpg --keyserver certserver.pgp.com --send-key blake@cyb.org
gpg: success sending to 'certserver.pgp.com' (status=200)
There are several popular keyservers in use around the world.
The major keyservers synchronize themselves, so it is fine to
pick a keyserver close to you on the Internet and then use it
regularly for sending and receiving keys.
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Validating other keys on your public keyring
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Daily use of GnuPG