Security in Computing (3rd Edition)

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©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 1 CS 161: E-commerce October 24, 2005 ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 2 Stages in E-commerce purchase Stages in E-commerce purchase ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 3 Stages in e-commerce purchase Stages in e-commerce purchase Advertising Solicitation Negotiation Purchase Payment Delivery Ordering/support ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 4 Credit cards as an enabler Standard purchase model reveals credit information Overhead costs can be high for microtransactions Acquiring Bank vs. Consumer Bank Payment processors ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 5 Why is a credit card transaction 50¢? Why is a credit card transaction 50¢? Account acquisition & credit processing Incoming interchange Cardholder billing Payment processing Cardholder servicing & promotion Issuer center administration Overlimit & collections Cardholder authorizations Card issuing Issuer fraud investigations ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 6 Information goods Information goods Consider the purchase of an information good or service: Library information Search services Software Video clips These transactions may be large value or microtransactions In either case, atomicity is crucial
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©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 7 Payment methods: Atomicity ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 8 What Is atomicity? What Is atomicity? I won’t try to give a formal definition 3 types of atomicity: Money atomicity All money transfers complete with non-ambiguous results Money is neither destroyed nor created Goods atomicity One receives goods if and only if one pays Example: Cash On Delivery parcels Certified delivery Both buyer and seller can prove the delivered content If you get bogus goods, you can prove it ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 9 First Virtual First Virtual Credit Card Acquirer Merchant Consumer Internet User pays after receiving goods Money atomicity only Messages sent in clear Uses expensive credit card transactions First Virtual ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 10 Netscape/SSL model Netscape/SSL model Internet Credit Card Acquirer Encrypted “tunnel” through the Internet Private Line Consumer sends card # direct to merchant Similar to today’s phone order Must trust merchant with card info Weak atomicity High transaction costs Merchant Consumer ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 11 Third party intermediary model (Cybercash) Third party intermediary model (Cybercash) Credit Card Acquirer Encrypted “tunnel” through the Internet Merchant Consumer Internet Protects consumer’s card info Use Internet for reaching Cybercash gateway to acquirers Adds to credit card card cost Cybercash ©2005 by J. D. Tygar , cs.161.org, 24 Oct 2005 12 Mastercard/Visa SET Mastercard/Visa SET Encrypted “tunnels” through the Internet Merchant Consumer Internet Protects consumer’s card info by cryptography Money-atomicity only
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