COMP 102 Lecture Notes - Lecture 21: Key Distribution, Prime Number, Depth Perception

• School: McGill University
• Department: Computer Science (Sci)
• Course: COMP 102
• Professor: Daniel Pomerantz

Document Summary

Recap: edge/corner detecion, object recogniion, depth percepion. Today cryptography: caesar shif, permute encrypion, public key v. private key encrypion, storing password on cpu"s. The irst encrypion julius caesar: the oldest encrypion. To take the leters and shif them by the certain leters in order. Punctuaion remains the same/ we loop at the end of the alphabet. Subsituion cipher: using a permute encrypt- every character gets mapped to a diferent, random character, brute force -> factorial possibility -> ineicient, analyze the common leters. Enigma: wwii: subsituion cipher, the subsituion patern changed for each word. This req 26 (25) #: not everyone can encode the message. Given x & y, z is easy to calculate. Mod operaion remainder: 8 = 5 (mod 3) b/c 8/3 = 2 remainder 2; 5/3 1 remainder 2. Key distribuion: we choose 2 prime numbers: p and q, p*q = n, we then calculate 2 numbers in f(n) -> e|public and d|private.