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Quantum Bit Commitment

Quantum Bit Commitment. Christian Schaffner DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science NAT-årsfest June 3, 2005. Alice. Bob. Alice & Bob. *!¤. Alice. Bob. Divorce Problems. *!¤. who gets the house?. Alice. Bob.

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Quantum Bit Commitment

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  1. Quantum Bit Commitment Christian Schaffner DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science NAT-årsfest June 3, 2005 A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  2. Alice Bob Alice & Bob *!¤ A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  3. Alice Bob Divorce Problems *!¤ who gets the house? A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  4. Alice Bob Coin-Flipping over the Telephone It’s tails, I get the house! A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  5. Alice Bob A Coin-Flipping Protocol not random! A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  6. Alice Bob The Solution A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  7. Alice Bob The Explanation A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  8. commit Alice Bob Bit-Commitment Scheme Bob‘s view open • important cryptographic primitive • hiding • binding A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  9. Alice Bob Particular Bit-Commitment Scheme commit to 0 Bob‘s view (n MegaBytes) commit to 1 bounded memory! (n MB) open • honest Alice needs: n • cheating Alice needs: 2¢n • Memorycheater< 2 ¢ Memoryhonest ) binding • perfectly hiding A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  10. Alice Bob Quantum Bit-Commitment Scheme Bob‘s view measure qbits in basis a n quantum bits bounded quantum memory! bounded memory! open classically: Memorycheater< 2 ¢ Memhonest • perfectly hiding • honest Alice needs no quantum memory • Memorycheater< n/2 ) binding A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

  11. bounded quantum memory! bounded quantum memory! Alice Bob The End *!¤ A A R H U S U N I V E R S I T E T DAIMI – Department of Computer Science BRICS – Basic Research in Computer Science

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