# Lecture: Introduction to Cryptography and Cryptanalysis

### Background Material

- String manipulation
- Probability distribution

### Reading

- Sections 1.1, 1.6 and 1.7 of the text.

### Topics

- Terminology: cipher, plaintext, ciphertext, alphabet, encryption,
decryption, key, symmetric key cryptography, adversary,
cryptanalysis, ciphertext only attack, known plaintext attack,
chosen plaintext attack, brute force attack.
- Shift cipher
- Monoalphabetic substitution ciphers
- Frequency analysis
- Introduction to Maple, string processing, and substitution cypers.
See sub.mw.

### Lecture Notes

### Resources

### Assignments

This assignment is a practice assignment not intended to be handed in.
- Write a program to determine the frequencies of digraphs occurring
in the book War and Peace
Display frequencies as a matrix where the (r,c) intry is the probability that c follow r.
- Attempt to solve several cryptograms from
Scott Bryce's
Cryptogram page.
- Download and install Maple from the IRT software site and review
the worksheet from the lecture - sub.mw.

Created: Apr. 3, 2012 (revised Sept. 19, 2016) by jjohnson AT cs DOT drexel DOT edu