* 8 *

Object orientation

Self-test questions

  1. Explain what is meant by private channel and covert channel. Consider the following functions in C++:
    void function(int a, int b)            void function(int& a, int& b)
    {                                      {
    ...                                    ....
    }                                      }
    Which of these functions has a private channel to the calling function and which has a covert channel? What does this mean?
  2. Global variables can also be considered as a means for covert communication. Explain how the careless use of global variables can lead to errors in program code.
  3. Compare the Clarke-Wilson model idea of using specialized programs to provide access control with the use of specialized class-methods in C++ or Java.

Graded problems - group work

This week the practical work is an experiment which has several purposes Your group must finish and submit all its grades/reports within two weeks of this week's lecture.

Each group has submitted the first part of the project as a signed file. The signatures have been removed from the files so that they are anonymous, and each group has been given three other groups' projects to review. You have been given three projects at random. Your task is to:

  1. Look at the three projects which have been assigned to your group and use the refereeing form below to comment briefly on the work. You should also assign an overall score from 0-5, where 5 is best, to say what you thought of the project. For completing your reviews seriously, your group will receive course credit.

    Review group-login

    Enter the login name and password of one person in your group

    and the login names of all the others

    Login name 1: Password:
    Login name 2: Password:
    Login name 3: Password:
    Login name 4: Password:

  2. For the second part of your group's project, discuss the security of the procedure you have just undertaken.