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Quantum key distribution devices:

How to make them and how to break them


PhD Thesis Defense
Sarah Kaiser
Institute for Quantum Computing

Information security is an integral part of modern society.

Classical infrastructure is already horribly compromised.

Attacks on classical key exchange will only get worse.

At least many people are Shor...

Potentially Secure Key Exchange

Post-quantum cryptography

Quantum key distribution

Why don't we all have quantum keys?

  1. Distance/Loss: $\approx 300$ km

  2. Hardware developments

  3. Realistic device security models

One approach:
QKD receiver satellite

How to make them and how to break them

  1. Distance →
    Modeling for airborne QKD

  2. Hardware →
    Robust quantum optical components

  3. Security models →
    Novel laser damage attack on commercial system

Distance:

Getting to space is costly

Test platform candidates

High altitutde balloon
Aircraft, Doctor Killer

Model risk assessment

GOAL:
establish a QKD link with parameters representative of a modeled, night satellite pass.
METRICS:

Link time [s] → $\approx 250$
angular velocity [˚/s] → {0.7,1.2}
Raw key rate [kHz] → $\approx 1$

Stratospheric balloons

Google Maps
Timmins Timmins
Visual assessment Modeled
Altitude threshold
Altitude
Flight # Timmins Visual Altitude
1
2
3
4
5
6
7
Fail (< 5 min)
High risk (< 30 min)
Moderate risk (< 60 min)
Low risk (> 60 min)

Plane constraints

Bonanza luggage door
Geometry model

Comms test flights

test flights

Infrastructure:

robust devices up to the task

QKD receiver satellite

Reciever payload schematic

Single photon detector unit

detector unit
Geometry model

Integrated optical assembly (IOA)

IOA schematic
IOA photo

Acquisition pointing and tracking (APT)

detector unit
Geometry model

QBER

QBER

Security:

Functionality $\neq$ security

How do we use a sledgehammer to pick a lock?

No demonstrated successful countermeasures!

How we made them and how I broke them

  1. Distance →
    Modeling for airborne QKD

  2. Hardware →
    Robust quantum optical components

  3. Security models →
    Novel laser damage attack on commercial system