V. Find answers to the following questions

1) What is asymmetric cryptography called?

2) What is the principal difference between public and private key?

3) What is the main difference between symmetric and asymmetric cryptography?

4) What are the main branches of the public key?

5) How can the central problem for public key cryptography be solved?

6) How can you break an algorithm?

7) Why do we use digital signatures?

8) How can you achieve authentication?

9) Do all asymmetric key algorithms operate the same way?

VI. Look at these phrases from the text and explain the underlined parts in your own words

1) The private key is kept in secret, while the public key may be widely distributed.

2) ... a message encrypted with a recipient’s public key can be decrypted…

3) This is used to ensure confidentiality.

4) If another user can successfully decrypt it using the corresponding public key…

5) Then she sends the box to Bob through regular mail.

6) … which he has obtained previously, maybe by a face-to-face meeting …

7) The critical advantage in an asymmetric key system is …

8) This prevents a third party from copying a key while…

VII. Define the following terms

infrastructure, host, protocol, vendors, access restrictions, private, registration, circuit switching, duration, release, intermediate, node

VIII. Make sentences using the following phrases

1) to lose sensitive reports

2) there is always a chance that

3) a reliable backup solution

4) is also implemented

5) the combination is often referred to

6) to protect hardware mechanisms

7) personal or corporate data

IX. Use an appropriate word from the list below to fill in the gaps

a) user f) important k) authority p) encrypted

b) replace g) advantage l) multi-user q) certification

c) cryptosystems h) vulnerable m) secure r) primary

d) adversary i) techniques n) cryptography s) necessary

e) secret-key j) password j) private t) algorithm

Public-key cryptography may be 1) _____ to impersonation, however, even if users’ 2) _____ keys are not available. A successful attack on a 3) _____ authority will allow an adversary to impersonate whomever the 4) _____ chooses to by using public-key certificate from the compromised authority to bind a key of the adversary’s choice to the name of another 5) _____.

In some situations, public-key cryptography is not 6) _____ and secret-key cryptography alone is sufficient. This includes environments where secure

7) _____ agreement can take place. It also includes environments where a single 8) _____ knows and manages all the keys. Since the authority knows everyone’s keys already, there is not much 9) _____ for some to be “public” and others “private”. Also, public-key 10) _____ is usually not necessary in a single-user environment. For example, if you want to keep your personal files 11) _____ , you can do so with any secret-key encryption 12) _____ using, say, your personal 13) _____ as the secret key. In general, public-key cryptography is best suited for an open 14) _____ environment.

Public-key cryptography is not meant to 15) _____ secret-key cryptography, but rather to supplement it, to make it more 16) _____. The first use of public-key 17) _____ was for secure key exchange in an otherwise secret-key system; this is still one of its 18) _____ functions. Secret-key cryptography remains extremely 19) _____ and is the subject of ongoing study and research. Some secret-key 20) _____ are discussed in the sections on Block Ciphers and Stream Ciphers.