Foundations of Cyber Security II

In preparation of the main exam tomorrow, here are a few notes.

1. The exam will be held in the GHH (E2.2). We will start at 10 sharp, so make sure to be there in time.

2. We have released a seating plan, which you can find in the materials section. Please, check ahead of time where you are sitting for an orderly process tomorrow.

 

Do not forget to bring your student ID and a non-erasable pen for writing. You are allowed one hand written cheat sheet (size A4) and may use an English/German dictionary.

Dear students,

the main exam of CySec2 will be next week Tuesday at 10:00. In order to participate in the exam, you need to register in LSF until tomorrow.

You are permitted to take part in the exam, if you got at least 89 points, which 93 of you did. We have entered all points of the exercise sheets into CMS and you can see your eligibility on your status page.

This week there will be tutorials at the usual time slots. They will cover side channels, the side channel project, and any exam preparation topics you want them to cover.

A few announcements regarding the exercise sheets:

• Task 9.4 of sheet #9 contains a task that you cannot solve yet. You thus do not have to provide a solution to it. We will add +2 points to your submission if (!) you obtain at least 1 point for any other task of sheet #9.
• Exercise sheet #10 will be the last graded sheet of CySec II. As it is slightly larger than usual, you can start working on it already today (= now). You can find it in CMS, as usual, just three days earlier. We will offer office hours next week Mon-Wed in which you can ask questions. Find the exact time slots on the exercise sheet.
• You will need 89 points overall (sheets 1-10) to be admitted to the CySec II exams.

Due to the public holiday on Thursday there will be no tutorials next week.

We offer two timeslots for office hours instead. You can use these to ask the tutors about all topics.
The office hours take place on Tuesday from 16:00 to 18:00 in seminar room 107 (E1.3) and on Wednesday from 12:00 to 14:00 in lecture hall 003 (E1.3).

We were informed of a problem with the exercise 06. The problem manifest itself in receiving fewer bytes then send to the server by the client.

The problem happens if the uplink connection of the client is not quick enough and not all the data arrives at the same time. Then the server only reads and returns partial data. To fix the issue, we updated the binary to wait one second, to allow all data to be read at the same time.

--- a/exercises/exercise06/code/bufoverflow.c
+++ b/exercises/exercise06/code/bufoverflow.c
@@ -58,6 +58,7 @@ void echo_everyone() {

         if (pid == 0) { /* child */
             alarm(30);
+            sleep(1);
             echo_client(client_sock);
             shutdown(client_sock, SHUT_RDWR);
             close(client_sock);

The updated source code and binary can be downloaded from the Materials section.

We have updated some of the slides of the OS Basics (03) lecture. In particular:

• Multi-level page tables: We added an example that better illustrates how addresses are used to dive into the various level of the page table, starting from an octal representation of the virtual address (3 octal numbers represent 9 bits, i.e., one level).
• Cache organization: There's now one extra slide that contains a formula and two examples how to compute the corresponding cache index and tags from a physical address. This reflects the (corrected) formula on the blackboard in today's lecture's repetition.

We have just assigned you to the CySec II tutorial slots, see CMS. Although we had to move the Wed tutorial to Thu due to a time conflict, we still made everyone happy (85% got their first tutorial choice, and 15% got a favorable option). Tutorials will start in the week after Easter, i.e., April 23-25. The first week will cover a recap of the lectures and an extra voluntary exercise sheet. The first mandatory exercise sheet will be handed out after this week's lecture.