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Anonymity in Electronic Commerce

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					Balancing Privacy and
   Accountability
              Yiannis Tsiounis




                     GTE Laboratories, Inc.
Privacy in context

Data secrecy
  Voice/messages, transaction amounts, credit
   card #s, merchant info, etc
Personal information
  Identity/name of users, other personal info
This talk: personal information
Legal requirements

Voting
Auctions
Handling confidential info
  Healthcare environments
  Electronic toll booths
  Cellular calls
  Signing proprietary documents
Marketability

Anonymous payments (e-cash)
  Retain anonymity of cash
Anonymous e-mails
  Already in use

Anonymous identities
  General use
The flip side:
Regulating anonymity
Criminal behaviour
  Multiple voting, e-mail abuse, blackmailing,
   money laundering, defaulting in auctions, etc.
Accountable transactions
  Tax purposes, locate individuals
Convenience
  Loss of personal data ( “key recovery”)
Tracing model

Trustee
  Judge, Government, Board of Trustees,
   Consumer organizations, or any combination
Augmenting basic system
  Encrypting personal info with Trustee’s public
   key
  Verify correctness of this encryption (by a
   Delegate of the Trustee)
Requirements

Trustee only involved at tracing
  Delegate used to enforce traceability
Efficiency
Selectivity
  Privacy revocation should be on a “per case”
   basis
Additional issues
  Blackmailing in cash - “distress cash”
Settings

(Blind) Digital signatures
Electronic cash
Group signatures
Anonymous identities
Digital signatures

Blindly sign a document
  Useful for a notary public, Health Care
   privacy
  Building block for more complex protocols
Be able to recover blinded document if
 necessary
Technical solution:
 Provide the signer with an encrypted copy
Magic ink digital
signatures

               Trustee

                         Decrypt

                  Encrypted
                  Document
      Signer




                         User
                                   Signed
                                   Doc
Electronic cash

                     Trustee
 Coin Tracing                  Owner Tracing


      Encrypted
      Coin
                     Bank

                                        Encrypted
                                        ID
         User                  Shop
                                        Coin
       (Anonymous)
       Coin
E-Commerce applications

Substitute physical “cash”
Provide anonymity for the legitimate users
              And
Traceability for the Government
Assurance for lost coins
Blackmailing prevention
Group signatures

               Trustee

                         Identify group member



               Manager

                                     Encrypted
                                     Private Key
  Member                    User
                                    Signed Document
 (Anonymous)                        (With Group's
 Private Key                        Public Key)
Applications

Signing company documents, while:
  Concealing internal structure (signer)
  Allowing CEO/Board of Trustees to trace
   signer
Controlled access to confidential data
  The party authorizing access is anonymous
  A Trustee can revoke the anonymity
Anonymous identities
(Pseudonym creation)

                Trustee

                              Identify user



                Issuer (CA)

                                               Encrypted
                                               Credentials
       User                      Verifier
                                              Identity
  (Anonymous)
                                              (Signed by Issuer)
  Credentials
Applications
Anonymous e-mail/message posting
Auctions
Anonymous transactions (stock trading)
Retain anonymity
  Court (witnesses, defendants)
  Everyday transactions
  Healthcare
Challenges

Crossing international boundaries
Legal precedence
Consumer acceptance
Infrastructure