1. 1 Original Message Scrambled Message Public Key receiver Internet Scrambled+Signed Message Original Message Private Key receiver The Process of Sending Messages Using Public Key Cryptography How Digital Signature Technology Works? Sender Receiver Message Digest + Private Key of sender Public Key sender to reveal Message Digest Hash

2. 2 Symmetric Key Algorithms DES (Data Encryption Standard) – 56 bits DES (Data Encryption Standard) – 56 bits IDEA (International Data Encryption Algorithm (IDEA) – 128 bits IDEA (International Data Encryption Algorithm (IDEA) – 128 bits RC2 – (block cipher) 1-2048 bits RC2 – (block cipher) 1-2048 bits RC4 (stream cipher) – 1-2048 bits RC4 (stream cipher) – 1-2048 bits Rinjdael – 128-256 bits Rinjdael – 128-256 bits

3. 3 Attacks on Symmetric Key Algorithms Key Search Attacks Key Search Attacks Cryptanalysis Cryptanalysis System-based Attacks System-based Attacks

4. 4 Public Key Algorithms DSS – Digital Signature Standard based on DSA (Digital Standard Algorithm) DSS – Digital Signature Standard based on DSA (Digital Standard Algorithm) RSA RSA Elliptic Curves Elliptic Curves

5. 5 Electronic Payment Systems Credit-card based payment systems Credit-card based payment systems Electronic checks Electronic checks Electronic cash Electronic cash Micro-payment systems – Milicent, Payword etc. Micro-payment systems – Milicent, Payword etc.

6. 6 Issuer Bank Cardholder Account Acquirer Bank Merchant Account Card Brand Card Holder 1.Issue Credit Card Merchant 2. Show Credit Card 4. Capture 3. Authorization 1.Issue Credit Card 6. Amount Transfer 5. Payment Request

7. 7 VirtualPIN Payment System

8. 8 Buyer 2. Account ID Valid? 3. Account OK! 5. Transaction Details 1. Account ID 4. Information Goods 6. Satisfied? 7. Accept/Reject or Fraud Indication Web Server (Selling Goods) Web Server (Selling Goods) First Virtual Internet Payment System Server Buying with First Virtual