1. CSCI-235 Micro-Computers in Science Privacy & Security

2. Simplified Communications Model - Diagram

3. Encryption Encryption is the coding and scrambling process by which a message is made unreadable except by the intended recipient Encryption is needed for electronic commerce Encryption Basics A readable message is called plaintext An encryption algorithm is a formula used to make plaintext unreadable The coded message is called ciphertext I LOVE YOU V YBIR LBH

4. Symmetric key encryption are encryption techniques that use the same key to encrypt and decrypt a message Strong encryption refers to encryption methods that are used by banks and military agencies and are nearly impossible to break

5. Basic Terminology plaintext - the original message ciphertext - the coded message cipher - algorithm for transforming plaintext to ciphertext key - info used in cipher known only to sender/receiver encipher (encrypt) - converting plaintext to ciphertext decipher (decrypt) - recovering ciphertext from plaintext cryptography - study of encryption principles/methods cryptanalysis (codebreaking) - the study of principles/ methods of deciphering ciphertext without knowing key cryptology - the field of both cryptography and cryptanalysis

6. Symmetric Cipher Model

7. Two requirements for secure use of symmetric encryption a strong encryption algorithm a secret key known only to sender / receiver Y = E K (X) X = D K (Y) Assume encryption algorithm is known Implies a secure channel to distribute key

8. Classical Substitution Ciphers Where letters of plaintext are replaced by other letters or by numbers or symbols Caesar Cipher Earliest known substitution cipher By Julius Caesar First attested use in military affairs Replaces each letter by k-th letter on Example ( what is k ? ): meet me after the toga party PHHW PH DIWHU WKH WRJD SDUWB

9. Can define transformation (with k = 3) as: a b c d e f g h i j k l m n o p q r s t u v w x y z D E F G H I J K L M N O P Q R S T U V W X Y Z A B C Mathematically give each letter a number a b c d e f g h i j k l m 0 1 2 3 4 5 6 7 8 9 10 11 12 n o p q r s t u v w x y Z 13 14 15 16 17 18 19 20 21 22 23 24 25 Then have Caesar cipher as: Y = E K (X) = (X + k) mod 26 X = D K (Y) = (Y – k) mod 26 EXAMPLE: Encrypt “howdy” using key k = 5

10. Cryptanalysis of Caesar Cipher Only have 26 possible ciphers A maps to A,B,..Z Could simply try each in turn A brute force search Given ciphertext, just try all shifts of letters

12. Privacy in Cyberspace Privacy refers to an individual’s ability to restrict the collection, use, and sale of confidential personal information The Internet is eroding privacy through the selling of information collected through Web sites Few laws regulate selling personal information

13. Cookies Cookies are small text files that are written to an individual’s hard drive whenever a Web site is visited File is sent back to the server each time you visit that site Stores preferences, allowing Web site to be customized Stores passwords, allowing you to visit multiple pages within the site without logging in to each one Tracks surfing habits, targeting you for specific types of advertisements Legitimate purposes of cookies include recording information for future use. Example: retail sites using “shopping carts” Questionable practices include banner ad companies tracking a user’s browsing actions and placing banner ads on Web sites based on those actions

14. Hacker Someone who attempts to gain access to computer systems illegally Hacker noun (see Raymond, 1991) A person who enjoys learning the details of computer systems and how to stretch their capabilities – as opposed to the most users of computers, who prefer to learn only the minimum amount necessary One who programs enthusiastically or who enjoys programming rather than just theorizing about programming

15. First Network Hack (Telephone) John Draper (AKA Cap’n Crunch) 1970’s Free long distance calls using a whistle found in a cereal box Whistle emits the same frequency as AT&T long lines to indicate a line was ready to route a new call (2600 Hz)

16. Flaw: AT&T took cost cutting measures The signaling and voice used the same circuit This flaw made the system vulnerable to anybody that can generate 2600 Hz Solution: Now signaling takes place on a separate path from the one you talk on