Network Security Exercise #1

Network Security Exercise #1 Falko Dressler and Christoph Sommer Computer and Communication Systems Institute of Computer Science, University of Innsbruck, Austria 11.5.2011 Falko Dressler and Christoph Sommer: Network Security Exercise #1 1 / 19

Proseminar First of all: welcome! Requirements Registration for the PS Active ZID (Linux) account Basic C/C++ programming skills Falko Dressler and Christoph Sommer: Network Security Exercise #1 2 / 19

Proseminar Objectives of the proseminar: Hands-on experiences In-depth study of some lecture topics In case of questions, please do ask! Drop by our offices or simply send emails! Schedule: Wednesday, 10:15am 11:45am, RR 22 Thursday, 10:15am 11:45am, RR 22 Falko Dressler and Christoph Sommer: Network Security Exercise #1 3 / 19

Home work Home work Once per week, announcement during the proseminar and on the web site Group work! Programs in C/C++ check for buffer overflows! Submission and evaluation Latest by Tuesday, 11:59pm via the dedicated scp system Presentation of selected solutions and discussion Falko Dressler and Christoph Sommer: Network Security Exercise #1 4 / 19

Credits and grading All the exercises including home work must be completed in time(!) Keep in mind that the proseminar is organized in form of group work The grade will reflect both the discussions in the proseminar and the completed exercises Falko Dressler and Christoph Sommer: Network Security Exercise #1 5 / 19

Topics in the Proseminar Enigma RSA, modes of encryption Hash collisions WEP OpenSSL IPSec Spoofing MIX networks Firewalls Monitoring Falko Dressler and Christoph Sommer: Network Security Exercise #1 6 / 19

Our scp submission system We are now setting up working groups (2 3 students per group) We need to set up the group account Falko Dressler and Christoph Sommer: Network Security Exercise #1 7 / 19

Attack Trees Formal method to model threats on a (computer) system Possible attacks can be visualized in form of a tree: The root is the final objective Edges represent necessary steps to achieve this goal Can be used for security analysis of a system Security estimation (How secure is my system?) What-if questionnaire Cost estimation... Falko Dressler and Christoph Sommer: Network Security Exercise #1 8 / 19

Example Open safe Pick lock (I) Learn combo Cut open safe (P) Install improperly (I) Find written combo (I) Get combo from target Threaten (I) Blackmail (I) Eavesdrop Bribe (P) Listen to conversation (P) Get target to state combo (I) from Bruce Schneier, Attack Trees Modeling security threats. Dr. Dobbs Journal, December 1999 Falko Dressler and Christoph Sommer: Network Security Exercise #1 9 / 19

Example Marking all impossible actions Open safe Pick lock (I) Learn combo Cut open safe (P) Install improperly (I) Find written combo (I) Get combo from target Threaten (I) Blackmail (I) Eavesdrop Bribe (P) Listen to conversation (P) Get target to state combo (I) from Bruce Schneier, Attack Trees Modeling security threats. Dr. Dobbs Journal, December 1999 Falko Dressler and Christoph Sommer: Network Security Exercise #1 10 / 19

Example Estimating costs Open safe ($10 K) Pick lock ($30 K) Learn combo ($20 K) Cut open safe ($10 K) Install improperly ($100 K) Find written combo ($75 K) Get combo from target ($20 K) Threaten ($60 K) Blackmail ($100 K) Eavesdrop ($60 K) Bribe ($20 K) Listen to conversation ($20 K) Get target to state combo ($40 K) from Bruce Schneier, Attack Trees Modeling security threats. Dr. Dobbs Journal, December 1999 Falko Dressler and Christoph Sommer: Network Security Exercise #1 11 / 19

Enigma The term Enigma is Greek, meaning riddle Invented by Arthur Scherbius (1878 1929) Primarily used during World War 2 by the German army More than 200 000 machines have been produced Falko Dressler and Christoph Sommer: Network Security Exercise #1 12 / 19

Picture Falko Dressler and Christoph Sommer: Network Security Exercise #1 13 / 19

Internal Structure 5 different rotos, can be arbitrarily used Each rotor has 26 positions Additional plug connections to swap characters Key concept: each input character must not map to the same character in ciphertext Encryption process is the same as decryption Falko Dressler and Christoph Sommer: Network Security Exercise #1 14 / 19

Code Books Falko Dressler and Christoph Sommer: Network Security Exercise #1 15 / 19

Code Books Falko Dressler and Christoph Sommer: Network Security Exercise #1 16 / 19

Weaknesses 2 10 23 different keys assuming 3 out of 5 rotors, plug connections, and two possible reflectors, which roughly translates to a key length of 77 bit The period of the middle and leftmost rotors are too long Some issues with the reflector Effective key length of 22 bit Falko Dressler and Christoph Sommer: Network Security Exercise #1 17 / 19

Cryptanalysis Polish mathematician Marian Rejewski deciphered the rotors using permutation theory in 1932 Some weaknesses in using the Enigma, e.g., submission of the rotor start positions in encrypted form Mechanical decoding became possible The Polish submitted their information to the British in 1939 Alan Turing invented the bomb in 1940 More than 30000 radio messages have been deciphered Currently preserved in Hut 6 in Bletchley Park Falko Dressler and Christoph Sommer: Network Security Exercise #1 18 / 19

Copyleft Slide 13: Wikipedia, User Littlejoe, GNU Free Documentation Licence Slides 14, 17, 18: Wikipedia, GNU Free Documentation Licence Slides 15, 16: Copyright (c) 2008 Frode Weierud, http://cryptocellar.web.cern.ch/cryptocellar/enigma/ Falko Dressler and Christoph Sommer: Network Security Exercise #1 19 / 19