# After-gate attack on a quantum cryptosystem

@article{Wiechers2010AftergateAO, title={After-gate attack on a quantum cryptosystem}, author={Carlos Wiechers and Lars Lydersen and Christoffer Wittmann and Dominique Elser and Johannes Skaar and Ch. Marquardt and Vadim Makarov and Gerd Leuchs}, journal={New Journal of Physics}, year={2010}, volume={13}, pages={013043} }

We present a method to control the detection events in quantum key distribution systems that use gated single-photon detectors. We employ bright pulses as faked states, timed to arrive at the avalanche photodiodes outside the activation time. The attack can remain unnoticed, since the faked states do not increase the error rate per se. This allows for an intercept–resend attack, where an eavesdropper transfers her detection events to the legitimate receiver without causing any errors. As a side…

## 147 Citations

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## References

SHOWING 1-10 OF 23 REFERENCES

### Faked states attack on quantum cryptosystems

- Computer Science, Mathematics
- 2005

A new type of attack on quantum cryptography systems is proposed. In this attack, Eve utilizes various optical imperfections in Bob's scheme and constructs light pulses so that Bob does not…

### Trojan-horse attacks on quantum-key-distribution systems (6 pages)

- Computer Science, Mathematics
- 2006

It is shown that all systems must implement active counter measures, including an auxiliary detector that monitors any incoming light, to reduce the maximal information gain that an adversary can gain using Trojan-horse attacks.

### Quantum key distribution with high loss: toward global secure communication.

- Computer Science, PhysicsPhysical review letters
- 2003

A decoy-pulse method to overcome the photon-number-splitting attack for Bennett-Brassard 1984 quantum key distribution protocol in the presence of high loss by intentionally and randomly replacing signal pulses by multiphoton pulses (decoy pulses).

### Experimental demonstration of time-shift attack against practical quantum key distribution systems

- Physics
- 2007

This result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability $(\ensuremath{\sim}4%)$ to break the security of the system.

### Decoy state quantum key distribution.

- Physics, Computer SciencePhysical review letters
- 2005

The method is to use decoy states to detect eavesdropping attacks and has the best of both worlds--enjoying unconditional security guaranteed by the fundamental laws of physics and yet dramatically surpassing some of the best experimental performances reported in the literature.

### Security of quantum key distribution with imperfect devices

- Computer ScienceInternational Symposium onInformation Theory, 2004. ISIT 2004. Proceedings.
- 2004

This paper prove the security of the Bennett-Brassard (BB84) quantum key distribution protocol in the case where the source and detector are under the limited control of an adversary. This proof…

### Beating the photon-number-splitting attack in practical quantum cryptography.

- Physics, Computer SciencePhysical review letters
- 2005

We propose an efficient method to verify the upper bound of the fraction of counts caused by multiphoton pulses in practical quantum key distribution using weak coherent light, given whatever type of…

### Controlling passively quenched single photon detectors by bright light

- Physics
- 2009

Single photon detectors (SPDs) based on passively quenched avalanche photodiodes can be temporarily blinded by relatively bright light, of intensity less than 1 nW. A bright-light regime suitable for…

### The security of practical quantum key distribution

- Computer Science
- 2009

Essential theoretical tools that have been developed to assess the security of the main experimental platforms are presented (discrete- variable, continuous-variable, and distributed-phase-reference protocols).

### Practical scheme to share a secret key through a quantum channel with a 27.6% bit error rate

- Physics
- 2002

A secret key shared through quantum key distribution between two cooperative players is secure against any eavesdropping attack allowed by the laws of physics. Yet, such a key can be established only…