Manifest: Monday 5 September 2001

Assignments Due
Monday, 10 September	Problem Set 1
Monday, 1 October	Projects Preliminary Proposal

Readings
Read before 10 September: MBC, Chapter 6.

Vigenere Square

                  1         2         3         4         5
Count:   12345678901234567890123456789012345678901234567890123456         
Plain:   ThebiggerboysmadeciphersbutifIgotholdofafewwordsIusually 
Key:     KEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKE
Cipher:  DLCLMEQIPLSWCQYNIASTFOVQLYRSJGQSRRSJNSDKJCGAMBHQSYQEEJVC
            6         7         8         9        10        11
         7890123456789012345678901234567890123456789012345678901234
Plain:   foundoutthekeyTheconsequenceofthisingenuitywasoccasionally
Key:     YKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEY
Cipher:  DYYLNSSDXFOOCIXFOGMXWCAYCXGCYJRRMQSREORSSXWGEQYGAKWGYRYVPW
             12        13        14        15        16
         5678901234567890123456789012345678901234567890123456789
Plain:   painfultheownersofthedetectedcipherssometimesthrashedme
Key:     KEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYK
Cipher:  ZEGXJSVXFOSUXIPCSDDLCNIROGROHASTFOVQCSKOXGWIQDLPKWFOHKO
        17        18        19        20
         012345678901234567890123456789012345
Plain:   thoughthefaultlayintheirownstupidity - Charles Babbage (quoted in The Code Book)
Key:     YKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKEYKE
Cipher:  XFYYERXFOJYEPRVEWSRRRIGBSUXWRETGNMRI

Links

• Alex Biryukov's lecture notes on cryptanalysis of Enigma
• Alan Turing's Treatise on Enigma (1940, declassified in 1996)
• Bletchley Park
• Enigma Movie, Breaking the Code movie
• Password Recovery, Microsoft Money 2.0 and Quicken 3.0

Questions

• How to attack the Vigenere cipher
• How to calculate the keyspace for a mechanical cipher machine
• How to factor permutations that are products of involutions

Propose to an Englishman any principle, or any instrument, however admirable, and you will observe that the whole effort of the English mind is directed to find a difficulty, a defect, or an impossiblity in it. If you speak to him of a machine for peeling a potato, he will pronounce it impossible: if you peel a potato with it before his eyes, he will declare it useless, because it will not slice a pineapple.

Charles Babbage, breaker of Vigenere cipher, after losing funding for his Difference Engine project, 1823.

University of Virginia Department of Computer Science CS 588: Cryptology - Principles and Applications

David Evans evans@virginia.edu