Beware that cryptography is widely (but inappropriately!) used as a synecdoche for cryptology. (This is not unlike the widely understood incorrect usage of the word hacker.) We will try to use these w...Beware that cryptography is widely (but inappropriately!) used as a synecdoche for cryptology. (This is not unlike the widely understood incorrect usage of the word hacker.) We will try to use these words more carefully. There will be very little number theory, but we will set up some terminology and simple examples of cryptography and the corresponding cryptanalysis, with an emphasis on the old, historic, systems which are no longer viable in the modern age.