DomainSpecific DBMS issues

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Domain-Specific DBMS issues

• Atomicity in Electronic Commerce
• Hao Xi

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Important Application Domains

• Geographic Information Systems (GIS) --
  Spatial information about cities, states,
  countries, etc.-- DBMS must be able to answer
  spatial queries
• Temporal and Sequence Databases-- Provide
  support for queries over sequences and temporal
  data-- Typical sequence query find the weekly
  moving average of the Dow Jones
  Industrial Average-- Typical temporal query
  find the longest interval in which the same
  professor teaches two courses

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Important Application Domains

• Images and Video Databases --
  Content-Based Image Retrieval-- Distributed
  Multimedia Databases-- Video-on-Demand
• Information Retrieval and Text Databases--
  Enable users to query a large volume of data--
  Queries based on keyword search-- Criteria
  precision recall-- Semistructured data HTML
  documents bibliography file

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Atomicity in Electronic Commerce by J. D. Tygar,
University of California
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Concepts for proper handling of E-commerce

• Atomic transactions
• Cryptographically secure protocols
• Secure computation
• Safe voting
• High reliabilityThis paper concerns with atomic
  transactions and discusses two highly atomic
  protocolsThe NetBill Protocol Cryptographic
  Postage Indicia

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Three Levels of Atomicity to Protect Electronic
Commerce Protocols

• Money atomicitytransfer of funds from one party
  to another without creating or destroying money
• Goods atomicitymoney atomic plus exact transfer
  of goods for money
• Certified deliverymoney and goods atomic
  protocols that also allow both a merchant and a
  customer to prove exactly which goods were
  delivered

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Non-atomic Electronic Commerce Protocols
Most of the proposed electronic commerce
protocols do NOT satisfy all three levels of
atomicity.

• Digicash use anonymous digital cash protocol
  not money atomic
• First virtual uses email to confirm transactions
  with customersfails goods atomicity
• Secure Socket Layer (SSL) set up secure
  communication channel by cryptography to transfer
  customers credit card number to the merchant
  may incur merchant fraud not goods atomic
• STT/SEPP/iKP customer digitally signs a purchase
  request with price and request is encrypted in a
  banks public key merchant submits sales request
  with price for the bank bank intermediate and
  make the deal if prices match prevent merchant
  fraud fails goods atomicity

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Two Highly Atomic E-Commerce Protocols

• NetBillProvides all three levels of atomic
  transactionsAn alpha version built at Carnegie
  Mellon
• Cryptographic Postage IndiciaPC generated laser
  printed indicia for postage metersDesigned for
  the Postal Service Information-Based
  ProgramAchieve money atomicity without using a
  central server

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NetBill Protocol

• Between 3 parties customer, merchant and NetBill
  server
• Outline of protocola) customer request price
  for goodsb) merchant makes offer to customerc)
  customer tells merchant that she accepts offerd)
  merchant sends the information goods encrypted by
  key Ke) customer sends signed EPO containing
  digital signed value for ltprice,
  cryptographic checksum of encrypted goods,
  time-outgt to merchantf) merchant
  countersigns EPO and signs the value of K. Both
  values are sent to NetBill serverg) NetBill
  server checks the signature and counter-signiture
  on EPO, checks customers account to ensure
  funds exist, and checks time-out value not
  expired. If all is OK, NetBill server
  transfers price funds from customers account to
  merchants. It stores K and the
  cryptographic-checksum of the encrypted
  goods. It then sends a signed receipt that
  includes K to merchanth) merchant records
  receipt and forwards it to the customer.
  Customer then decrypt her encrypted goods.

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Three Levels of Atomicity Achieved
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Cryptographic Postage Indicia

• achieved money atomicity without using a central
  server via the help of secure hardware (i.e. any
  attempt to penetrate them will result in erasure
  of all information stored inside them).
• application PC generated indicia electronic
  wallet
• outline1) use a secure hardware to store an
  account balance for postal customers2) account
  decremented whenever postage is printed3) secure
  hardware prepares a cryptographically signed
  message that contains (sender address,
  receiver address, date sent, sequence number).
  Information printed on envelope using an
  efficient data representation such as PDF-4174)
  At potal sorting facility, data block is checked
  to see if they match the address used for
  sorting and to verify uniqueness of sequence
  number. Indicia remains valid for 6 months.
  The database at sorting station can regularly be
  purged of entries with a date older than 6
  months.

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Money Atomicity
An adversary attempt to break money atomicity by
forging indicia must do one of the two things

• copy existing indicia, which then will only be
  valid for the encrypted delivery address, and
  will be caught at the sorting station
• attempt to find the value used to digitally sign
  the cryptographic indicia, which will require
  opening the secure hardware, erasing all the
  vulnerable data within

Hence, money atomicity is preserved without using
a central server.
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Open Problems
Electronic Commerce has many open problems. Some
interesting ones are

• Can atomicity and anonymity be mutually
  compatible?
• What other atomicity models exist in electronic
  commerce besides money atomicity, goods atomicity
  and certified delivery? Is there a general
  schema?
• What is the minimum number of message exchanges
  necessary in an atomic purchase?
• Can we give a formal definition for atomicity?
• How can we prove that a protocol is atomic?

Note the paper was written in 1995. There may
well be breakthrough in answering some of these
questions.
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More Information ...

• PDF copy of the paper available at authors
  homepagehttp//www.cs.berkeley.edu/tygar
• NetBillhttp//www.ini.cmu.edu/netbill/
• cryptographic postage indiciahttp//www.cs.cmu/ed
  u/afs/cs/project/dyad/www/