OpenSSH Public Key Comments

OpenSSH public keys allow for an optional comment to follow the public key data. The comment may be customized via the -C option to ssh-keygen(1) when creating the keypair, or simply edited in the resulting keyfile. If exchanging a public key with a different group or company, alter the comment to remove the default user and host information. This avoids exposing internal host and usernames, and allows the addition of a timestamp, in the event the public key must be changed periodically.

$ ssh-keygen -t rsa -C "Example `date +%Y-%m-%d`" -f key
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in key.
Your public key has been saved in key.pub.
The key fingerprint is:
3e:2c:54:24:39:9d:ca:ad:c4:b6:32:c3:ce:a2:ea:cc Example 2007-03-24
$ cat key.pub
ssh-rsa AAAAB3Nza?qfgw== Example 2007-03-24