Any Leopard-compatible Macintosh is capable of setting a hardware password, using OpenFirmware for PowerPCs or Extensible Firmware Interface (EFI) for Intel-based machines. When enabled, hardware password protection blocks the ability to do the following:
- Use the C key to start up from an optical disc.
- Use the N key to start up from a NetBoot [...]

Authentication is the process of identifying an account or service, and verifying its right to perform a restricted operation. Mac OS X uses several different methods of authentication, along with separate subsystems. All system utilities tie into directory services to verify credentials.
For example, imagine a server with Open Directory accounts and a FileMaker Pro server [...]