1. Efficient Device-Independent Quantum Key Distribution
Esther Hänggi Renato Renner Stefan Wolf
ETH Zürich
EUROCRYPT 2010
31st May 2010

2. Quantum Key Distribution1 1
'Traditional' QKD relies on:
- Laws of Quantum Mechanics
- Exact Specification of Devices

3. Why Device-Independence?
45°
45° 1 1
need to trust devices + manufacturer
Example: BB84 Entanglement-based [BBM92] ([E91])
Other measurements or systems
insecure

4. Quantum Key Distribution1 1
no signaling
'Traditional' QKD relies on:
- Laws of Quantum Mechanics
no need to trust
manufacturer
- Exact Specification of Devices
- Security of Labs

5. Systems and Security

6. PXYZ|UVW PXYZ|UVW W Z U V Y X Systems and Security
random system [Maurer 02] U V Y
PXYZ|UVW
PXYZ|UVW X
Condition: no signaling
„shielded labs“

7. PXYZ|UVW W Z U V Y X Pr[XY=UV]=1- XY=UV Systems and Security
4-insecure
secure
[Barrett,Hardy,Kent 05]: different system
0 0
0 1
1 0
1 1
U V
X Y → or
But: - inefficient
Privacy amplification?
- noise-intolerant
[BBR98],[ILL99]

8.    Privacy Amplification 4 4 4 individual attacks
general attacks
[HRW08]
individual attacks
[AGM06][SGBMPA06]
[AMP06]  4  4  4

9.     Privacy Amplification 4 (4)n 4 4
general attacks + no signaling
within labs
[Masanes 09] (non-constructive)
[this paper]: XOR deterministic
privacy amplification function  4 
(4)n  4  4

10. The Protocol
- measure

11. PXY|UV   The Protocol - measure - check correlation
- information reconciliation
(random linear code)
PXY|UV
- privacy amplification 
secure key

12. Conclusion Secure key - against most general attacks
- universally composable
- works based on (observable) violation
of Bell Inequality
- ONLY requirement: no signaling
- device-independent
Open question: relaxing of no signaling condition?

13. Thank you
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