1. 1 Secure Credit Card Transactions on an Untrusted Channel Source: Information Sciences in review Presenter: Tsuei-Hung Sun ( 孫翠鴻 ) Date: 2010/9/24

2. 2 Outline Introduction Motivation Scheme Security analysis Performance evaluation Advantage vs. weakness Comment

3. 3 Introduction Credit cards based payment system Entity: customer, merchant, credit card issuer and bank. Credit card: credit card number, Card Verification Value (CVV). Transaction: billing digest, information about the customer.

4. 4 Introduction Secure Socket Layer (SSL) – Establish a trusted connection between two parties. HTTPS (Secure HTTP) – Send messages securely using SSL. Both two need public keys and certificates, besides, the operations process are complex.

5. 5 Motivation SSL and HTTPS are complex because they involve key-management, user credentials and certificates. Smart cards require extra infrastructure like smart card reader and middleware. This paper want to let the transaction become more simpler and easy to achieve security.

6. 6 Scheme (ex. customer credit card data) Credit card confidentially Common key K BMi

7. 7 Scheme UI1: customer related non critical data. UI2: importance to the merchant data. h = H CVV (UI1, UCI, T, CVV) T: time stamp. UCI : customer critical information. CVV: Card Verifier Value. T ID : transaction id. r c and r m : response values generated by the issuer. T ID = H(h,UI1,T) 1.Request phase 2.Verification phase 3.Authentication Phase 4.Response Phase

8. 8 Scheme Authentication Phase – Issuer has a database containing customer credit card data. A1 Retrieve CVV and UCI from database. A2 Compute hash value h1. A3 Comparing h and h1 consistency. A4 Generate response values A5 Send acknowledgement to bank. Reject: Accept: : common key between the bank and the merchant i.

9. 9 Security analysis Replay Attack Forgery Attack Man-in-the-Middle Attack Guessing Attack

10. 10 Performance evaluation Complexity Comparison Request phase: exor operation, hash operation (bank). Verification phase: hash operation (merchant), intersection operation (issuer). Authentication phase: exor operations (issuer).

11. 11 Advantage vs. weakness Advantage – Can resist 4 type important attack. – No need complex computing. – No need extra overhead like smart card, reader and middleware. – Just use hash function and a common key. – just use a one round protocol. Weakness – Common key may be weak.