Day 2: Computer Science Lesson in Cryptology

The final lesson of the morning hinged on the study of communicating using protocols that afford information security, data confidentiality and integrity, and require authentication.  Prof. Greer led this discussion and explored various cryptographic methods utilized throughout history.

The Caesar cipher (or Caesar code) has been widely used because of its simplicity.  It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.  For example, with a left shift of 3, the letter "D" would be replaced by "A", "E" would become "B", and so on. The method is named after Julius Caesar, who used it in his private correspondence.

The Vigenere cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword

A cryptogram is a type of puzzle that consists of a short piece of encrypted text.  Generally the cipher used to encrypt the text is simple enough that the cryptogram can be solved by hand.  "E" is good letter to help solve cryptograms because most English words end with "E", occurring in that fashion almost 13% of the time.

ASCII is a another character-encoding scheme originally based on the English alphabet.  One can encode strings of text based on numerical equivalents.  This encoding scheme assists computers in translating human text to machine readable code and vice-versa.