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Anonymous Digital Cash

Anonymous Digital Cash. Ashok Reddy Madhu Tera Laxminarayan Muktinutalapati (Lux) Venkat Nagireddy. Overview. What is digital cash? Need for anonymous digital cash Concepts in anonymous digital cash Protocol: Dining Cryptographers’ protocol Achieving anonymity Illustration

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Anonymous Digital Cash

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  1. AnonymousDigitalCash Ashok Reddy Madhu Tera Laxminarayan Muktinutalapati (Lux) Venkat Nagireddy

  2. Overview • What is digital cash? • Need for anonymous digital cash • Concepts in anonymous digital cash • Protocol: Dining Cryptographers’ protocol • Achieving anonymity • Illustration • Practical concerns • Conclusion

  3. What Is Digital Cash? • Digital cash is a digitally signed payment message that serves as a medium of exchange

  4. Need for Anonymous Digital Cash • Increase in electronic surveillance by governments and other institutions • Lack of privacy features associated with ordinary electronic transactions

  5. Concepts in Anonymous Digital Cash Anonymity is chiefly concerned with • Unlinkability • Untraceability

  6. Protocol • Dining cryptographers’ protocol

  7. Dining Cryptographers…(2) • Model

  8. Achieving Anonymity • Blind digital signatures • Blinding factor

  9. Illustration • The Digital Bank would offer electronic bank notes: messages signed using a particular private key • The electronic bank notes could be authenticated using a corresponding public key • The bank would also make public, a key to authenticate electronic documents sent from the bank to its customers

  10. Illustration…(2) • To withdraw a dollar from the bank, Alice generates a note number (each note bears a different number, akin to the serial number on a bill); she chooses a 100-digit number at random • Before sending the note number to the bank for signing, Alice multiplies it by a random (blinding) factor • Now she signs the number with the private key corresponding to her "digital pseudonym"

  11. Illustration…(3) • After receiving the blinded note signed by the bank, Alice divides out the blinding factor and uses the note as before • The blinded note numbers are, therefore, "unconditionally untraceable"

  12. Practical Concerns • Counterfeiting or Double-spending: Fraudulently spending the same money more than once Remedy: • Checking each note against an on-line central list when it is spent • Using tamper-resistant hardware (called an "observer") • Generating blinded notes that require the payer to answer a random numeric query about each note when making a payment

  13. Practical Concerns…(2) • Framing: An attempt by a bank to fraudulently claim that a customer has double-spent the same piece of cash when the customer hasn’t. Remedy: • Similar to those discussed earlier

  14. Practical Concerns…(3) Other concerns: • Theft • Adaptability

  15. Conclusion • Anonymous cash is "unconditionally untraceable" which provides enough privacy to the user • A system (implementing anonymous digital cash) closely resembling our current payment system will be easier for consumers to understand and adapt to

  16. Questions?

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