There is only one file type that uses the .KDB extension:
Keypass Database File
Database of passwords used by KeePass Password Safe, a free, open-source password management program; stores user passwords for a variety of logins, such as network logon, e-mail, FTP, websites, etc; passwords within the database can be sorted into groups for further organization.
KeePass Password Safe was originally developed for Windows, but has been ported to Linux and Mac OS X under the name "KeePassX."
Updated: January 16, 2008