Explain the difference between an attack surface and an attack tree. (At least 1 paragraph) Explain the difference between a private key and a secret key. (At least 1 paragraph) Describe and explain, at least, seven different physical characteristics that are used for authentication in biometric applications. (At least half a page) Explain Federated Identity (Identity Federation), how it is different from Single Sign-On (SSO) and give an example of how it is used commercially. (At least half a page).