# TMA4160 Cryptography - Fall 2018

 Lecturer: Assistant: Schedule Kristian Gjøsteen Herman Galteland Tuesday 14-16 El4 Thursday 12-14 El4 Monday 8-9 A3-138 Realfagbygget Thursday 1415-1500 848 in SBII December 15

## Messages

15/1: The exam results: A - 11, B - 10, C - 10, D - 11, E - 6, F - 3.

Some comments on the different problems:

• 1 A few people tried to be clever instead of using exhaustive search. However, sometimes exhaustive search is the right thing to do. This is one of those cases; being clever probably took longer than doing an exhaustive search. (Clever or not, the grades are the same.)
• 2b As usual, many people insist on annoying me by doing exponent arithmetic modulo 47 instead of 46.
• 4a Several people read the problem as asking for rows whose coordinates added up to zero modulo 2. Tsk, tsk. Also, some people found columns, not rows.
• 5 A lot of people wanted the given map on pairs of field elements to be a group homomorphism, because CRT gives us a ring isomorphism. This is (sort of) what we are trying to prove in this problem, so it cannot simply be assumed. (It is true because of the algebraic nature of the elliptic curve addition.)

15/12: Today's exam with suggested solutions.

## What you should know before taking the course

You should be familiar with basic abstract algebra such as groups, rings and fields.

It is helpful, but not required, to know something about computational complexity and the analysis of algorithms. Using a computer algebra system (or equivalent) is required for some of the exercises. Previous experience with computer algebra systems is helpful, but not required.

## Course material

Lecture notes:

• These notes follow the lectures fairly closely, but will be updated throughout the course.

Main book:

Supplements:

You should be able to get by with just the lecture notes (and possibly the supplements), but many of you will find Stinson useful. Note that Stinson does not cover the entire curriculum.

The curriculum is defined to be the material covered by the lecture notes, the lectures and the exercises.