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Form different parts of speech and translate them.



Cipher

Give as many word combinations as possible and translate them

key

solution

Make the word combinations

1. ciphertext-only a) a DES key
2. flipped b) ciphertext
3. hill climbing c) aids
4. trial d) the process
5. recover   e) bit results
6. mimic f) of discrete elements
7. incomprehensible g) solution
8. chain h) algorithm
9. automated i) group
10. superencipherment j) key

Complete the text using the terms and word combinations given below.

Running through, a strong encryption algorithm, maps, in parallel, the cryptanalyst, the actual message, computing power

There are several distinct types of cryptoanalytic attack. The type used depends on the type of cipher and how much information ….. has.

Types of cryptoanalytic attacks.A standard cryptoanalytic is to determine the key which … a known plaintext to a known ciphertext. This plaintext can be known because it is standard or because it is guessed. If the plaintext segment is guessed it is unlikelely that its exact position is known however a message is generally short enough for a cryptoanalyst to try all possible positions … . In some systems a known ciphertext-plaintext pair will compromise the entire system however … will be unbreakable under this type of attack.

A brute force attack requires a large amount of … and a large amount of time to run. It consists of trying all possibilities in a logical manner until the correct one is found. For the majority of the encryption algorithms a brute force attack is impractical due to the large number of possibilities.

Another type of brute force attack is a dictionary attack. This essentially involves … a dictionary of words in the hope that the key (or the plaintext) is one of them. This type of attack is often used to determine passwords since people usually use easy to remember words.

In a ciphertext only attack the cryptanalyst has only the encoded message from which to determine the palintext, with no knowledge whatsoever of …. A ciphertext only attack is presumed to be possible, if not easy. In fact, an encryption techniques resistance to a ciphertext only attack is considered the basis for its cryptographic security.

Complete the text.

Given a block of known plaintext, and its corresponding … , starting with a random 56-bit possible key, do the following:

· … the known plaintext with that key, and with every one of the 56 other keys obtained by inverting one bit of that key.

· Compare the resulting ciphertext to the … ciphertext.

· In those of the 56 cases where the flipped bit results in the ciphertext produced … in fewer bits from the actual ciphertext than that produced by the original trial key, invert that bit of the trial key to obtain the next trial key.

This is a simple example of a … algorithm, where the number of bits by which a trial encipherment differs from the actual ciphertext is a measure of one's (lack of) altitude.

Translate into English the following passage.

Осуществляя атаку, криптоаналитик может ставить целью решение следующих задач:

1. Получение открытого текста из зашифрованного.

2. Вычисление ключа шифрования.

В общем случае, вторая из перечисленных задач является существенно более сложной, чем первая. Однако, имея ключ шифрования, криптоаналитик может впоследствии расшифровывать все данные, зашифрованные найденным ключом. Такая атака (в случае ее успешного осуществления) называется полным раскрытием алгоритма шифрования.

Атаки на алгоритмы шифрования принято классифицировать в зависимости от того набора информации, который имеет злоумышленник перед осуществлением своей атаки.

Text 2. Read the text and write its summary. Point out the facts that are new for you. Present them orally.





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