“What You Know”

Keypads and coded locks are in wide use as a method of access control. They are reliable and very user friendly, but their security is limited by the sharable and guessable nature of passwords. They have familiar phone-like buttons where users punch in a code — if the code is unique to each user it’s called a personal access code (PAC) or personal identification number (PIN). Keypad generally implies the ability to accept multiple codes, one for each user; coded lock usually refers to a device having only one code that everyone uses.

The security level of keypads and coded locks can be increased by periodically changing codes, which requires a system for informing users and disseminating new codes. Coded locks that don’t have their code changed will need to have their keypad changed periodically if a detectable pattern of wear develops on the keys. As with access cards, keypad security can be increased by adding a biometric to confirm user identity.