UPAI: A Universal Payment Application Interface

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U-PAI A Universal Payment Application Interface

• A paper from Second USENIX Workshop on Electronic
  Commerce, USENIX, Oakland, CA

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Outline

• Introduction
• API Definitions
• Sample Ecash Proxy
• Conclusions

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Introduction

• Many payment mechanisms nowadays
• e.g. First Virtual, CyberCash, Ecash, SET,
• The most significant difference is the order of
  steps required to execute a payment

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Introduction (2)

• Diversity of payment mechanisms stymied the
  progress of electronic commerce
• customers must maintain accounts with several
  different payment mechanisms
• no standard way for payment mechanisms to
  interact with application software

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U-PAI

• U-PAI, a universal payment application interface
• Goal define a common set of functions that act
  as a layer of abstraction between application
  software and payment mechanisms

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U-PAI abstracts payment mechanism internals
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API Definitions

• CORBA specification in ISL of Xerox PARC?s ILU
• Three main objects
• AccountHandle
• PCR (Payment Control Record)
• Monitor

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AccountHandle

• This instance is a representation of a real-world
  account
• The user wishes to start making electronic
  payments with the account
• Query balance and credit limits on the account

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Analogy to clarify the notion of accounts and
AccountHandle
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AccountHandle (2)

• Internal fields
• Balance
• CreditLimit
• AccountType
• TransferAccountTypesFrom
• TransferAccountTypesTo

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AccountHandle (3)

• Methods
• OpenAccount(PropertySet acctinfo) Any
• CreateAccount(PropertySet acctinfo) Any
• CloseAccount()
• DeleteAccount()

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PCR (Payment Control Record)

• This instance is a representation of a single
  payment transaction
• the locus of control for all activities regarding
  that payment

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PCR (2)

• Internal fields
• RefID, ContextID
• Amount
• DestAccountHandle, SourceAccountHandle
• Status
• MonitorList

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PCR (3)

• Methods
• StartTransfer()
• TryToAbortTransfer()
• UpdateStatus(StatusEntry stat)

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Monitor

• To supplement the status tracking feature of a
  PCR
• Internal field status
• Method Notify(PCR p, StatusEntry s)

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Location of system components in the system
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Sample First Virtual Proxy

• The first service which allowed consumers to
  transfer real money across the network
• User?s credit card information is obtained in a
  secure, out-of-band channel
• Try before you buy philosophy

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First Virtual
FV Merchant Account
Application
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Merchant Monitor
Customer Monitor
Application
Payment Control Record
FV Customer Account Handle
FV Merchant Account Handle
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Sample Ecash Proxy

• An electronic coin-based payment mechanism
• Provides anonymity for the purchaser
• U-PAI interacts with ecash at the level of the
  user operations

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Ecash
Merchant Application
Customer Application
Merchant E-cash Client
Customer E-cash Client
Bank E-cash Server
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Merchant Monitor
Customer Monitor
Application
Payment Control Record
Merchant E-cash AccountHandle
Customer E-cash AccountHandle
Merchant E-cash Client
Customer E-cash Client
Bank E-cash Server
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Conclusions

• U-PAI allows a variety of payment mechanisms to
  be accessed by the same interface
• U-PAI only covers the basic functionality of
  accounts and payments

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The End