Tel-Aviv University

School of Computer Science

Introduction to Modern Cryptography

0368.3049

Fall Semester 2013/2014

# News

### Your graded assignment 4 can be picked up from mailbox 372

(30 Jan 2014 17:37)

### Your graded assignment 3 can be picked up from mailbox 372

(25 Jan 2014 18:47)

### Previous Exams

Moed_A_2008

Moed_B_2008

Moed_A_2010

Moed_B_2010

Questions you should skip:

2010.A: 1

2010.B: 3

2008.A: 2

2008.B: 3

In 2007.A.4: add the assumption p-1,q-1 don't divide each other. (At some point we said the latter is not needed, but it is. You can find the full solution here.)

As already said, in previous years, the course might have focused on different subjects and thus also the exams.

(16 Jan 2014 22:20)

### Example questions

Here are some example questions towards the exam. As Benny said, a previous e-mail, this year the course covered several different topics comparing to past years, which naturally affects the nature of the exam.

I intend to solve these questions (or at least some of them) in the recitation on Thursday 16 Jan. You can find the solution here.

(13 Jan 2014 08:06)

### You can submit assignment 4 on 19 Jan

The assignment is short, and a week should be enough. However, if you prefer you can submit on Sunday 19 Jan, instead of Thursday 16 Jan.

(09 Jan 2014 22:35)

### Recitation on Thursday 9 Jan is cancelled

Hi all,

I'm afraid I woke up sick and without a voice, so recitation today is cancelled. The material for today was supposed to be outside the scope of the course and the exam.

Sorry for the short notice

Nir

p.s.: I was planning to tell you about program obfuscation. If enough of you are interested I'll be happy to arrange a meeting at a different time.

(09 Jan 2014 06:35)

### Assigment 4 is posted.

The assignment is considerably shorter the previous ones. Thus, you are given a week to submit it.

(08 Jan 2014 18:22)

### Yet another correction to assignment 3 (guidance part).

In the guidance to question 3.b, $A'$ has to be a bit more careful, and in fact, the probabilistic analysis is a bit delicate.

Hence, we replaced the two of the items with easier items of the same weight. We made the previous ones a bonus, and augmented the guidance. Those of you who already solved the tricky ones (now the bonus ones), don't need to redo the easier ones, you will get both the basic and the bonus credit. Thanks to Naor for pointing out the problem in the original guidance!

(26 Dec 2013 12:49)

### Another correction to assignment 3

In 5.c:

You should show that $A'$ breaks $(\epsilon/(t+1),1)$-unforgeability, and not $(\epsilon/t,1)$.

(25 Dec 2013 06:34)

### Misprints in assignment 3.

We fixed a few misprints and clarified some things in assignments 3:

1. In question 1, $m\in \{0,1\}^*$.

2. In question 2, you should show that the scheme is $2\varepsilon$-semantically secure (rather than $\varepsilon$). Also, clarified what $\epsilon$-HCB means for trapdoor functions.

3. In question 3, (a) it should have been $A'^{E_{sk}(\cdot)}$ (the **'** was missing). (b) there was a "c" superscript that didn't make sense.

(23 Dec 2013 11:28)

### Your graded assignment 2 can be picked up from mailbox 372

$\hspace{1cm}$

(18 Dec 2013 11:53)

### Assignment 3 is posted.

The assignment is slightly longer than usual. You are given 3 instead of 2 weeks.

(18 Dec 2013 08:11)

### No lecture on 10/12 and lecture instead of recitation on 12/12

- Due to the Weizmann distinguished lectures day, there will be no class on tuesday 10/12. (You are all invited, but need to notify the organizers by email asap.)
- On Thursday, instead of a recitation, there will be a lecture. (It will be the same one-hour lecture played twice back-to-back, in the usual software engineering 104 room).

(04 Dec 2013 14:38)

### Deadline for assignment 2 has been postponed to Sunday 7 Dec

Good luck.

(04 Dec 2013 14:26)

### Two points about assignment 2

- In question 6, there was a misprint. You should find all degree 3 polynomials that factor into 3 linear factors (and not 4 of course).
- Two additional hints about question 7.c:

- It's enough to choose $N=\frac{2(\log\log p+\log4)}{\delta^2}$.
- For any events $A_1,\dots,A_k$, it holds that $\Pr[A_1\vee A_2\vee\dots\vee A_k]\leq \Pr[A_1]+\Pr[A_2]+\dots+\Pr[A_k]$. (Known as "union bound".)

(30 Nov 2013 10:54)

### Your graded assignment 1 can be picked up from mailbox 372

$\text{}$

(27 Nov 2013 17:36)

### Assignment 2 is posted.

Due Dec 5.

(20 Nov 2013 15:33)