Keeping your blog secure is extremely important these days. So much so that new installs of WordPress ask the user to create four security keys. These keys help ensure that the cookies placed in your browser when logged in are not easily de-coded by would be hacker sites. Some pre-existing installs of WordPress may only have one or two security keys while others may have none.
“Beginning with Version 2.6, three (3) security keys, AUTH_KEY, SECURE_AUTH_KEY, and LOGGED_IN_KEY, were added to insure better encryption of information stored in the user’s cookies. Beginning with Version 2.7 a fourth key, NONCE_KEY, was added to this group.
You don’t have to remember the keys, just make them long and complicated or better yet, use the online generator. “