Authenticity with Secrecy TO SEND A MESSAGE THAT IS SIGNED SECRETLY, THE SENDER MUST USE ENCRYPTION TWICE. TO SEND A MESSAGE, BOB: ENCRYPTS IT WITH HIS PRIVATE KEY AS A SIGNATURE, THEN ENCRYPTS THE RESULT WITH ALICE'S PUBLIC KEY FOR PRIVACY. WHEN SHE RECEIVES A MESSAGE, ALICE: DECRYPTS THE MESSAGE WITH HER PRIVATE KEY TO MAKE IT ACCESSIBLE, DECRYPTS IT USING BOB'S PUBLIC KEY TO VERIFY ITS SOURCE, SAVES THE HALF-ENCRYPTED VERSION SO SHE CAN PROVE BOB SENT IT LATER.

The Web: Technologies and Techniques Links to other course pages: CS 105 Home Page CS 105 Lecture Schedule CS 105 On-line Discussion Group: All discussions Discussion relating to this lecture topic Williams College Department of Computer Science

This page is part of a section of lecture slides related to " Authentication " within the topic "Privacy Issues and Encryption". Other slides within this section and other sections of slides for the topic "Privacy Issues and Encryption" can be accessed using the links below. Electronic Privacy Threats Internet Eavesdropping Who can you Trust? Secure Web Communications Traditional Cryptography Encryption Basics Cryptographic Notation The Caesar Cipher Key-based Encryption Schemes Generalizing the Caesar Cipher More Notation Key Properties Vigenere Cypher Vigenere Cypher (cont.) The Key Distribution Problem Public Key Cryptography Public Key Cryptography Public Key Distribution The RSA Cryptosystem Some Details of the RSA Cryptosystem Some Details of the RSA Cryptosystem (cont.) Properties of the RSA Cryptosystem Authentication Authentication Authentication and the Internet Authentication and Cryptography Digital Signatures? Digital Signatures (cont.) Authenticity with Secrecy Certifying Authorities Certifying Authorities (cont.) Data Gathering vs. Privacy "Passive" Privacy Threats HTTP Protocol Headers Server Response Headers Web Browser Headers What are "Magic Cookies"? Magic Cookies Data Mining Passive Privacy and Encryption Techniques Digital Cash Anonymous Internet Financial Transactions Commutative Encryption Blank Bills Withdrawal Symptoms Making Money A Spending Spree