Tài liệu Electronic payment systems and security

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Chapter 8 Electronic Payment Systems and Security © Prentice Hall, 2000 1 Learning Objectives ❚ Describe typical electronic payment systems for EC ❚ Identify the security requirements for safe electronic payments ❚ Describe the typical security schemes used to meet the security requirements ❚ Identify the players and procedures of the electronic credit card system on the Internet ❚ Discuss the relationship between SSL and SET protocols © Prentice Hall, 2000 2 Learning Objectives (cont.) ❚ Discuss the relationship between electronic fund transfer and debit card ❚ Describe the characteristics of a stored value card ❚ Classify and describe the types of IC cards used for payments ❚ Discuss the characteristics of electronic check systems © Prentice Hall, 2000 3 SSL Vs. SET: Who Will Win? ❚ A part of SSL (Secure Socket Layer) is available on customers’ browsers ❙ it is basically an encryption mechanism for order taking, queries and other applications ❙ it does not protect against all security hazards ❙ it is mature, simple, and widely use ❚ SET ( Secure Electronic Transaction) is a very comprehensive security protocol ❙ it provides for privacy, authenticity, integrity, and, or repudiation ❙ it is used very infrequently due to its complexity and the need for a special card reader by the user ❙ it may be abandoned if it is not simplified/improved © Prentice Hall, 2000 4 Payments, Protocols and Related Issues ❚ SET Protocol is for Credit Card Payments ❚ Electronic Cash and Micropayments ❚ Electronic Fund Transfer on the Internet ❚ Stored Value Cards and Electronic Cash ❚ Electronic Check Systems © Prentice Hall, 2000 5 Payments, Protocols and Related Issues (cont.) ❚ Security requirements ❙ Authentication: A way to verify the buyer’s identity before payments are made ❙ Integrity: Ensuring that information will not be accidentally or maliciously altered or destroyed, usually during transmission ❙ Encryption: A process of making messages indecipherable except by those who have an authorized decryption key ❙ Non-repudiation: Merchants need protection against the customer’s unjustifiable denial of placed orders, and customers need protection against the merchants’ unjustifiable denial of past payment © Prentice Hall, 2000 6 Security Schemes ❚ Secret Key Cryptography (symmetric) Keysender (= Keyreceiver) Original Message Sender Scrambled Message Internet Keyreceiver Scrambled Message Original Message Decryption Receiver Encryption © Prentice Hall, 2000 7 Security Schemes (cont.) ❚ Public Key Cryptography Public Keyreceiver Message Original Message Scrambled Message Private Keyreceiver Internet Scrambled Message Sender Receiver Private Keysender Digital Original Signature Message Original Message Scrambled Message Public Keysender Internet Sender Scrambled Message Original Message Receiver © Prentice Hall, 2000 8 Security Schemes (cont.) ❚ Digital Signature ❙ Analogous to handwritten signature Sender encrypts a message with her private key A digital signature is attached by a sender to a message encrypted in the receiver’s public key Any receiver with senders public key can read it The receiver is the only one that can read the message and at the same time he is assured that the message was indeed sent by the sender © Prentice Hall, 2000 9 Security Schemes (cont.) ❚ Certificate ❙ Identifying the holder of a public key (KeyExchange) ❙ Issued by a trusted certificate authority (CA) Name : “Richard” key-Exchange Key : Signature Key : Serial # : 29483756 Other Data : 10236283025273 Expires : 6/18/96 Signed : CA’s Signature © Prentice Hall, 2000 10 Security Schemes (cont.) ❚ Certificate Authority - e.g. VeriSign ❙ ❙ ❙ ❙ Public or private, comes in levels (hierarchy) A trusted third party services Issuer of digital certificates Verifying that a public key indeed belongs to a certain individual RCA BCA GCA CCA RCA : Root Certificate Authority BCA : Brand Certificate Authority GCA : Geo-political Certificate Authority CCA : Cardholder Certificate Authority MCA : Merchant Certificate Authority PCA : Payment Gateway Certificate Authority MCA PCA Hierarchy of Certificate Authorities Certificate authority needs to be verified by a government or well trusted entity ( e.g., post office) © Prentice Hall, 2000 11 Electronic Credit Card System on the Internet ❚ The Players ❙ Cardholder ❙ Merchant (seller) ❙ Issuer (your bank) ❙ Acquirer (merchant’s financial institution, acquires the sales slips) ❙ Brand (VISA, Master Card) © Prentice Hall, 2000 12 Electronic Credit Card System on the Internet (cont.) ❚ The process of using credit cards offline A cardholder requests the issuance of a card brand (like Visa and MasterCard) to an issuer bank in which the cardholder may have an account. A plastic card is physically delivered to the customer’s address by mail. The cardholder shows the card to a merchant to pay a requested amount. Then the merchant asks for approval from the brand company. The acquirer bank requests the issuer bank to pay for the credit amount. The authorization of card issuance by the issuer bank, or its designated brand company, may require customer’s physical visit to an office. The card can be in effect as the cardholder calls the bank for initiation and signs on the back of the card. Upon the approval, the merchant requests payment to the merchant’s acquirer bank, and pays fee for the service. This process is called a “capturing process” © Prentice Hall, 2000 13 Cardholder credit card Merchant Payment authorization, payment data Card Brand Company payment data account debit data payment data amount transfer Issuer Bank Acquirer Bank Cardholder Account Merchant Account Credit Card Procedure (offline and online) © Prentice Hall, 2000 14 Secure Electronic Transaction (SET) Protocol ❚ Sender’s Computer 1. The message is hashed to a prefixed length of message digest. 2. The message digest is encrypted with the sender’s private signature key, and a digital signature is created. 3. The composition of message, digital signature, and Sender’s certificate is encrypted with the symmetric key which is generated at sender’s computer for every transaction. The result is an encrypted message. SET protocol uses the DES algorithm instead of RSA for encryption because DES can be executed much faster than RSA. 4. The Symmetric key itself is encrypted with the receiver’s public key which was sent to the sender in advance. The result is a digital envelope. © Prentice Hall, 2000 15 Sender’s Computer Message   Sender’s Private Signature Key Message Digest Digital Signature + Message +  + Symmetric Key Encrypt Sender’s Certificate Receiver’s Certificate Encrypted Message  Encrypt Receiver’s Key-Exchange Key © Prentice Hall, 2000 Digital Envelope 16 Secure Electronic Transaction (SET) Protocol (cont.) ❚ Receiver’s Computer 5. The encrypted message and digital envelope are transmitted to receiver’s computer via the Internet. 6. The digital envelope is decrypted with receiver’s private exchange key. 7. Using the restored symmetric key, the encrypted message can be restored to the message, digital signature, and sender’s certificate. 8. To confirm the integrity, the digital signature is decrypted by sender’s public key, obtaining the message digest. 9. The delivered message is hashed to generate message digest. 10. The message digests obtained by steps 8 and 9 respectively, are compared by the receiver to confirm whether there was any change during the transmission. This step confirms the integrity. © Prentice Hall, 2000 17 Receiver’s Computer Receiver’s Private Key-Exchange Key Decrypt  Digital Envelope Message   Decrypt Symmetric Key Encrypted Message + + Sender’s Certificate Message Digest  compare  Decrypt Digital Signature Sender’s Public Signature Key © Prentice Hall, 2000 Message Digest 18 IC Card Reader Customer y Customer x With Digital Wallets Certificate Authority Electronic Shopping Mall Merchant A Merchant B Payment Gateway Protocol X.25 Credit Card Brand Entities of SET Protocol in Cyber Shopping © Prentice Hall, 2000 19 SET Vs. SSL Secure Electronic Transaction (SET) Secure Socket Layer (SSL) Complex Simple SET is tailored to the credit card payment to the merchants. SSL is a protocol for generalpurpose secure message exchanges (encryption). SSL protocol may use a certificate, but there is no payment gateway. So, the merchants need to receive both the ordering information and credit card information, because the capturing process should be initiated by the merchants. SET protocol hides the customer’s credit card information from merchants, and also hides the order information to banks, to protect privacy. This scheme is called dual signature. © Prentice Hall, 2000 20
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