Today is your first quiz!
It will be a written quiz taking the whole period. It will be closed-book. I will provide such things as the Vigenere square, multiplication table mod 26, english letter frequencies, and alphabet-to-number table, if needed.
- Use the Cryptosystem organizer to study the following cryptosystems (so this means being able to describe things like key space, how to encrypt/decrypt, being able to apply various cryptanalysis techniques). I may ask you to encrypt, decrypt, or cryptanalyse.
- Caesar cipher
- Scytale (no need for any cryptanalysis techniques beyond exhaustive search, but do know the system)
- Substitution cipher (alphabetic substitution)
- Vigenere cipher
- Affine cipher
- Hill cipher
- You should be adept at:
- modular arithmetic
- the notion of invertible element in modular arithmetic, finding inverses by inspection
- the notion of an invertible matrix in modular arithmetic
- notions of divisibility, primes, prime factorization, gcd, lcm
- performing the Euclidean algorithm and using it to find inverses in modular arithmetic (to be covered Friday Sept 2)
- Terminology you should be able to explain:
- coding theory
- plaintext and plaintext space
- ciphertext and ciphertext space
- key and keyspace
- types of cryptanalysis: ciphertext only, known plaintext, chosen plaintext, chosen ciphertext
- confusion (property of cryptosystem)
- diffusion (property of cryptosystem)
- On this quiz we won’t have any proofs, but in future ones, we will.
- You should know the broad outlines of the history, but I won’t test you on it.