SECURITY and CRYPTOGRAPHY 15-827 23 OCT 01 Lecture #11 M.B. 4615 Wean Recall: Our first (in-class) MIDTERM EXAM will be in two days, 25 OCTOBER. Like all my exams, that midterm will be closed book. In preparation for MidTerm Exam 1, do the following: 1. generate and learn by heart your own PRIVATE mapping from characters to digits. 2. Generate and practice your own PRIVATE protocol for mapping a CHALLENGE consisting of a word, phrase or sentence having at least 10 characters into a RESPONSE of at least 5 digits. 3. Write a program that is easy for Nick hopper@cs to run for turning CHALLENGES into RESPONSES using your mapping and your protocol. Prior to the Midterm, send Nick directions for running your program on challenges of his own choosing. For the Midterm itself, you will be given a collection of challenges which you must respond to in class. Your grade (FAIL = 0; PERFECT SCORE = 100) will be roughly PROPORTIONAL TO: 1. the number of correct digits in your response, plus 2. the time it takes us to break your protocol -- up to a maximum of 10 minutes -- but only if you are able to respond to each challenge in on average at most 30 seconds (think 15 seconds!), and INVERSELY PROPORTIONAL TO: 1. the time it takes you to respond to the challenges -- to be measured by your response time in class -- plus 2. the number of errors (i.e. number of digits in error) in your response. AN EXAMPLE: CHALLENGE = Just the place for a snark RESPONSE = 4 4 9 8 7 5 3 8 CHALLENGE = The bellman cried RESPONSE = 6 2 1 1 1 0 7 2 CHALLENGE = As he landed his crew RESPONSE = 0 5 9 9 4 2 0 0 CHALLENGE = with care RESPONSE = 5 6 9 1 0 4 5 8 CHALLENGE = Supporting each man RESPONSE = 1 1 5 4 6 9 4 3 CHALLENGE = on the top of the tide RESPONSE = 3 2 7 5 3 2 6 9 CHALLENGE = with a finger entwined RESPONSE = 6 9 2 0 4 0 1 3 CHALLENGE = in his hair RESPONSE = 1 3 0 1 6 4 0 1 CHALLENGE = Just the place for a Snark RESPONSE = 4 4 9 8 7 5 3 8 CHALLENGE = I have said it twice RESPONSE = 0 4 0 6 9 2 4 7 CHALLENGE = That alone should encourage RESPONSE = 2 0 4 9 1 1 7 2 CHALLENGE = the crew RESPONSE = 9 1 7 7 1 2 9 0 CHALLENGE = Just the place for a Snark RESPONSE = 4 4 9 8 7 5 3 8 CHALLENGE = I have said it thrice RESPONSE = 0 4 0 6 9 2 4 7 CHALLENGE = What I tell you three times RESPONSE = 1 7 2 1 4 7 4 9 CHALLENGE = Is true RESPONSE = 0 5 8 3 3 1 6 1