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Published bySheila Wilkinson Modified over 9 years ago
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Anonymous Digital Cash Ashok Reddy Madhu Tera Laxminarayan Muktinutalapati (Lux) Venkat Nagireddy
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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
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What Is Digital Cash? Digital cash is a digitally signed payment message that serves as a medium of exchange
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Need for Anonymous Digital Cash Increase in electronic surveillance by governments and other institutions Lack of privacy features associated with ordinary electronic transactions
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Concepts in Anonymous Digital Cash Anonymity is chiefly concerned with Unlinkability Untraceability
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Protocol Dining cryptographers’ protocol
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Dining Cryptographers…(2) Model
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Achieving Anonymity Blind digital signatures Blinding factor
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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
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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"
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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"
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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
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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
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Practical Concerns…(3) Other concerns: Theft Adaptability
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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
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Questions?
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