14. Grammar. Modal Verbs. See Grammar reference.

Grammar tasks

Task A. State the function of the following modal verbs.

1. Electronic Signatures can come in many forms.

2. The single-photon source and the detectors must be connected by a “quantum channel”.

3. Two forms of attack might be carried out.

4. A DMBS application may consist of one or more executable images and one or more data files.

5. High-quality signatures can offer authentication, integrity and non-repudation.

6. Could you help us?

7. Shall we stop working over this project?

8. I’m sure you should continue your research.

9. It must have been the developed algorithm we hadn’t met yet.

10. We believe our research group will be able to finish work in time.

Task B. Paraphrase the following sentences using the modal verbs given below.

1. I’m sure the paper is somewhere in the office. (must)

2. I think you are not working hard. (should)

3. I need this job! (must)

4. Perhaps our colleagues will come in time. It depends on the traffic. (might)

5. I’m sure the analysis is not ready. (can)

6. I think you don’t pay proper attention to the questions of security. (should)

7. It is forbidden to write your password anywhere! (must)

8. If you don/t know how to solve this problem, ask your colleagues to help you. (should)

9. The failure of the security system is not his fault. I’m sure in it. (can)

Task C. Write sentences using modal verbs and the following words. Comment on the modal verbs used in the sentences.

1. The idea/machine/generate speech/be discussed/for about 50 years.

2. The vulnerability analysis/take/five work days.

3. Employee/change/passwords.

4. I/help you/with the project?

5. Excuse me! You/explain this message for me?

6. While designing a network, consider how other components of its perimeter (intrusion detection systems, routers, and VPNs) / influence the security of infrastructure.

7. Block encryption algorithms / be used in a number of different modes, such as “electronic code book” and “cipher block chaining”.

8. Worms are programs that / run independently and travel from machine to machine across network connections.

15. Writing.

Write an abstract of the material you’d like to present at the conference (see Appendix 2).

16. Communication.

Find positive and negative examples of applying steganography in the life of the modern society.

Make a presentation to illustrate the facts you’ve found.

Prepare the report for the group conference and be ready to discuss it.

Unit 6. QUANTUM CRYPTOGRAPHY.

Pronunciation

Make sure you pronounce the following words properly:

quantum ['kwɔntəm]	qubit [kju:bɪt]
eavesdrop ['i:vzdrɔp]	mechanics [mɪ'kænɪks]
vibrate [vaɪ'breɪt]	angle ['æŋɡl]
vibration [vaɪ'breɪʃən]	discrepancy [dɪs'krepənsɪ]

Memorize the terms

1. Read the following terms and their definitions and memorize them:

be a bit off – be switched over, changed a bit

be bugged – be overheard

be on the lunatic fringe – be considered of minor importance, be ignored

discrepancy – difference, diversity

Eavesdrop – overhear, intercept

expand on an idea – study and speak in detail about an idea

insecure channel – unprotected channel that can be easily eavesdropped

measure – scale, determine

prearranged code – discussed beforehand

random result – probabilistic, patternless choice

2. Match the synonyms.

allow through	ruin
discrepancy	truncate
unauthorized	sequence
string	let pass
discard	difference
collapse	not having legal access

Reading

3. Pre-reading task.

Texts

What do you know about quantum cryptography and its application?

Comment on the efficiency of the quantum cryptography methods.

Can you name scientists and laboratories that conduct research in this sphere in Russia and abroad?

4. Text 1. Quantum cryptography. Find in the text the description of the phenomena of quantum mechanics.

Quantum cryptography is another kind of cryptography in this world. With it, you can create a communication channel where it is impossible to eavesdrop without disturbing the transmission. The laws of physics secure this quantum channel: even if the eavesdropper can do whatever he wants, even if the eavesdropper has unlimited computing power. Charles Bennett, Gilles Brassard, Claude Crepeau and others have expanded on this idea, describing quantum key distribution.

According to quantum mechanics, particles don't actually exist in any single place. They exist in several places at once, with probabilities of being in different places if someone looks. However, it isn't until a scientist comes along and measures the particle that it "collapses" into a single location. But you can't measure every aspect (for example, position and speed) of a particle at the same time. If you measure one of those two quantities, the very act of measuring it destroys any possibility of measuring the other quantity. The quantum world has a fundamental uncertainty and there's no way to avoid it.

That uncertainty can be used to generate a secret key. As they travel, photons vibrate in some direction; up and down, left to right or more likely at some angle. Normal sunlight is unpolarized; the photons vibrate every which way. When a large group of photons vibrate in the same direction they are polarized. Polarization filters allow only photons that are polarized in a certain direction through; the rest are blocked. For example, a horizontal polarization filter only allows horizontally polarized photons through. Turn that filter 90 degrees, and only vertically polarized photons can come through.

Let's say you have a pulse of horizontally polarized photons. If they try to pass through a horizontally polarized filter, they all get through. Slowly turn that filter 90 degrees; the number of photons getting through gets smaller and smaller, until none gets through. You'd think that turning the filter just a little will block all the photons, since the photons are horizontally polarized. But in quantum mechanics, each particle has a probability of suddenly switching its polarization to match the filter. If the angle is a little bit off, it has a high probability. If the angle is 90 degrees off, it has zero probability. And if the angle is 45 degrees off, it has a 50 percent probability of passing through the filter.