Artem Vakhitov tunes up eavesdropper's setup

New eavesdropping strategies in quantum cryptography

a master thesis done in Quantum Cryptography Project at the Department of Electronics and Telecommunications

Student:  Artem Vakhitov,
(exchange student from Department of Quantum ElectronicsSt. Petersburg State Technical University)
Supervisor (Norway):  Professor Dag Roar Hjelme
Supervisor (Russia):  Victor Tarkhanov,,
Delivered:  June 2000
Russian title:  Evaluation of security against unauthorized access for practical fiber-based quantum cryptosystems

This thesis was the first detailed study of a new class of eavesdropping strategies in quantum cryptography - conventional optical eavesdropping (also known as trojan horse attacks).

The results were subsequently published in a paper.


The thesis is written in Russian only. It's available in two formats: Artem Vakhitov in Quantum Cryptography lab


The thesis describes a new strategy of eavesdropping on quantum cryptographic systems, which eliminates the need of immediate interaction with transmitted quantum states. It allows the eavesdropper to avoid inducing transmission errors that disclose her presence to the legal users. As an object of the eavesdropping, phase-state fiberoptic schemes are considered.

In this eavesdropping strategy, settings of transmitting and/or receiving apparatus are interrogated by external high-power light pulses. Applicability conditions of this method are given. Type and amount of information learned by the eavesdropper is estimated, depending on parameters of the interrogating pulse and apparatus.

The thesis suggests security measures against this kind of attack.

Experimental setup for eaveadropping experiment is proposed and results of successful preliminary measurements are presented.

Also, the thesis contains a short review of existing methods, protocols and schemes of quantum cryptography.

The Lesson

Microphotograph of damage Phase modulator, cover removed
Result of electrical breakdown in phase modulator ($4,000+); detailed description

Never try to finish experiment in the last few days of student's stay. Damage to equipment will result. On the bright side, it might be photogenic. To be fair to Artem, I must admit that the other phase modulator of the two we had was broken by me (mechanically, during its internal modification).

We had a big trouble ordering replacement. Phase modulators with suitable specification were out-of-production by that time.

Artem Vakhitov sings


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