When you log into a computer with a username and password, you are using password authentication, a reliable method for identifying users. You can share your username with others, although the password remains a secret, as it uniquely identifies you to the computer. Password authentication provides a reasonable level of security at a low cost. Alternatives include biometrics, such as a fingerprint scanner; challenge/response where the computer prompts you for more information; and hardware, such as a keycard. Writer Bio
