A(n) ___________________ means the user has initiated an action that causes the program to perform the type of processing called for by the user's action.

If A and B each has an encrypted connection to a third party C, C can deliver a key on the encrypted links to A and B. A _________ center is responsible for distributing keys to pairs of users as needed.

Fill in the blank(s) with the appropriate word(s).

Windows 8's tile-based interface is called the Metro/Modern UI or _______________.

Fill in the blank(s) with the appropriate word(s).