Ex. 3 Look at these phrases from the text and explain the underlined parts in your own words

Date: 2015-10-07; view: 554.

Ex. 2 Find answers to the following questions

Ex. 1 Match the English - Ukrainian equivalents

1. limiting distribution a) сесія зв'язного структурного контролю

2. generic key в) зходимість алгоритму

3. power requirement с) втрата передачі

4. round-off error d) розвантаження, відкачка

5. communication area e) функціональна схема

6. algorithm convergence f) технологія надійних транзакцій

7. walkthrough session g) спільний ключ

8. translation loss h) граничний розподіл

9. scramble time i) помилка закруглення

10. key diagram j) необхідна потужність

11. swap-out k) конкурентний час

12. secure transaction technology l) область зв'язку

1. What is symmetric-key algorithm?

2. What terms are used for symmetric-key encryption?

3. What types are symmetric-key algorithms divided into?

4. Why are they used in modern cryptosystem designs?

5. Why is a quality asymmetric-key algorithm slower than a symmetric-key algorithm?

6. Why are keys subject to a cryptographic adversary?

7. How many keys are needed to ensure secure communications?

8. Why must encryption functions be reversible?

9. What way are book-ciphers implemented?

10. Why is a source of high entropy important?

1. … a class of algorithms for cryptography that use trivially related, often identical, cryptographic keys for both decryption and encryption.

2. ... in practice, represent a shared secret between two or more parties that can be used to maintain a private information link.

3. Use of the latter term can sometimes conflict with the term …

4. Stream ciphers encrypt the bits of the message one at a time, and block ciphers take…

5. both asymmetric (public) key and symmetric algorithms are used to take advantage of the virtues of both.

6. Symmetric-key algorithms are generally much less computationally intensive than asymmetric-key algorithms.

7. The disadvantage of symmetric-key algorithms is the requirement of a shared secret key, with one copy at each end.

8. Encryption functions must be reversible since you need to be able to both encrypt and decrypt messages.

9. For a more in-depth description of this method see Feistel cipher.

10. After several rounds of processing, the output becomes so scrambled that, in the case of well designed ciphers.

Ex. 4 Complete each gap in this text with a suitable word from the list

Traditional 1) _____ is based on the sender and receiver of a message knowing and using the same secret key. The sender uses the secret key to encrypt the 2) _____, and the receiver uses the same secret key to decrypt the message. This method is known as secret-key or 3) _____ cryptography. The main problem is getting the sender and receiver 4) _____ on the secret key without anyone else finding out. If they are in separate physical locations, they must trust some transmission medium to prevent the 5) _____ of the secret key being communicated. Anyone who 6) _____ or intercepts the key in transit can later read, modify, and forge all messages 7)_____ or authenticated using that key. The generation, transmission and storage of 8) _____ is called key management. All cryptosystems must 9) _____ key management issues. Because all keys in a secret key 10) _____ must remain secret, secret-key cryptography often has difficulty 11) _____ secure key management, especially in open systems with a large 12) _____ of users.

The concept of public-key cryptography was 13) _____ in 1976 by Whitfield Diffie and Martin Hellman. In their concept, each person gets 14) _____ of keys. Each person's public key is 15) _____ while the private key is kept secret. The need for the sender and receiver 16) _____ secret information is eliminated. The only requirement is that public keys are associated with their users in a 17) _____ (authenticated) manner. Anyone can send a 18) _____ message by just using public information, but the message can only be decrypted with a 19) _____ key, which is in the sole possession of the intended recipient. Furthermore, public-key cryptography can be used not only for 20) _____ (encryption), but also for authentication (digital signatures).

published keys encrypted cryptosystem

introduced providing a pair confidential

symmetric to share disclosure message

privacy cryptography number private

deal with trusted to agree overhears