MCS 150 Cryptanalysis Exam 2
Exam 2: Monday, January 20
This will be a closed-book and closed-notes exam.
You may, however, use a calculator.
Cryptanalysis aids, such as a Vigenere tableau,
will be provided.
You will have the entire class period to work the exam,
but you should not need all that time.
You should be prepared to solve problems of the following kinds.
- Encipher a message by ...
- normal Vigenere cipher
- Vigenere cipher with mixed plain/cipher sequences
- autokey with priming key letter
- Decipher a message enciphered by ...
- normal Vigenere cipher
- Vigenere cipher with mixed plain/cipher sequences
- autokey with priming key letter
- Demonstrate your ability to carry out and
interpret preliminary
cryptanalysis tasks like ...
- preparing a trigraph frequency distribution
- developing "Kasiski" (repeated sequences) evidence
- calculating indexes of coincidence
- calculating sums of products of frequency distributions
- using "slides" (matching frequency distributions)
- distinguishing monoalphabets from polyalphabets
- determining the length of the keyword for polyalphabetic
encipherment
- carrying out a probable word/known plaintext attack
- reducing a polyalphabetic encipherment to a monoalphabet
- Solve a not-too-hard polyalphabetic crypt.
- Answer questions on the video "Decoding Nazi Secrets."
Primary reference for study are your class notes and Sinkov chapter 3.
A supplementary reference is Lewand section 2.5.
Return home.