Getting Started with phpMyAdmin - Mastering phpMyAdmin 3.4 for Effective MySQL Management - page 8

With the lack of a configuration file, phpMyAdmin displays the cookie-based login
panel by default (more details on this in Chapter 2 , which explains that with the
default configuration, it's not possible to log in with an empty password):
We can verify this fact by opening our browser and visiting http://www.mydomain.
com/phpMyAdmin , and substituting the proper values for the domain part and the
directory part.
If we are able to log in, it means that there is a MySQL server running on the same
host as the web server ( localhost ), and we have just made a connection to it.
However, not having created a configuration file means that we would not be able
to manage other hosts through our installation of phpMyAdmin. Moreover, many
advanced phpMyAdmin features (for example, query bookmarks, full-relational
support, column transformation, and so on) would not be activated.
The cookie-based authentication method uses Blowfish encryption
for storing credentials in browser cookies. When no configuration file
exists, a Blowfish secret key is generated and stored in session data,
which can open the door to security issues. This is why the following
warning message is displayed:
The configuration file now needs a secret passphrase (blowfish_secret)