Commutative Encryption TO MAKE DIGITAL CASH POSSIBLE, WE MUST USE AN ENCRYPTION TECHNIQUE WHOSE ENCRYPTION AND DECRYPTION OPERATIONS ARE COMMUTATIVE. SUPPOSE ALICE ENCRYPTS M AND THEN BOB ENCRYPTS THE RESULT ALICE PRODUCED. IF THE ENCRYPTION TECHNIQUES USED ARE COMMUTATIVE, THEY BOTH HAVE TO DECRYPT TO GET THE MESSAGE BACK, BUT IT DOESN'T MATTER WHETHER ALICE OR BOB DECRYPTS FIRST. IF THE TECHNIQUES USED ARE NOT COMMUTATIVE, THEN BOB MUST DECRYPT FIRST FOLLOWED BY ALICE.

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This page is part of a section of lecture slides related to " Passive Privacy and Encryption Techniques " 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