In challenge-response authentication, both the User ID (i. e., message 1) and the Challenge (i. e., message 2) are in cleartext, but why is challenge-response authentication still a secure authentication method that can defeat replay attacks?

Write a method named addall that could be placed inside the hashintset class. this method accepts another hashintset as a parameter and adds all elements from that set into the current set, if they are not already present. for example, if a set s1 contains [1, 2, 3] and another set s2 contains [1, 7, 3, 9], the call of s1.addall(s2); would change s1 to store [1, 2, 3, 7, 9] in some order. you are allowed to call methods on your set and/or the other set. do not modify the set passed in. this method should run in o(n) time where n is the number of elements in the parameter set passed in.

In the context of the box model, what is the difference between a margin and a padding? a. a padding lies outside a box border, while a margin lies inside it. b. a padding lies inside a box border, while a margin lies outside it. c. a padding can be adjusted independently, while a margin depends on the size of its box. d. a padding depends on the size of its box, while a margin can be adjusted independently.

Janice usually works on a particular workbook that contains all business related data. she decides to keep a backup of all the data in a separate workbook. she opens a new workbook to transfer the data. which option should she use to copy all the data from one workbook to another workbook?