7. Give the English equivalents of the following words and word combinations.

фрагменты открытого текста; сдвиг; частотность букв; оставлены неизменными; сложный/изощренный; соотно­сить/сопоставлять; повторяющийся; основываться на ч.-л.; доступный/имеющийся в наличии; процесс шифрования/де­шифрования.

8. Give the Russian equivalents of the following words and word combinations.

Cyclical-shift substitution cipher, manual cryptography, keyword-based matrices, sets of characters, the reverse of the process, a brute force attack, reveal the private key, an iterative process, fractionation system, bilateral cipher, superencrypted by a transposition, a sequence of bits, to yield, adaptive chosen plaintext attack.

9. Supply the missing words where necessary.

In a substitution cipher the units of the plaintext are replaced ... other symbols. Double transposition ciphers ... keyword-based matrices were widely used. In a fractionation system a substitution is first made ... simbols ... the plaintext... multiple symbols of the ciphertext. Single letters or characters were the largest units that could be easily encrypted or decrypted ... hand. Systems which operated ... sets of three characters were proposed and understood ... potentially be more secure. Such systems were implemented ... because of the extra difficulty ... the manual encryption process. The encryption of any particular plaintext ... a block cipher will result... the same ciphertext when the same key is used. When a stream cipher is used the encryption process involves ... combin­ing ... the keystream ... the plaintext. A standard cryptoanalitic is ... determine the key which maps... a known plaintext... a known ciphertext. A brute force attack consists ... trying all possibilities ... a logical manner until the correct one is found.

10. Put the corresponding words and word combinations in the sentences.

Взломщик, перехватив закодированное послание Алисы; который доступен всем; выбранную атаку текста; подбор ключа; расшифровать или угадать; любой может отправить зашифрованное поедание Бобу; косвенно устанавливает отправителя; необходимы для того, чтобы соотнести человека и конкретный открытый ключ.

The use of public key cryptography is thus conceptually sim­ple. Bui two immediate worries may spring to mind. A first con­cern is that although ... will only see gibberish, the intruder knows both the key (Bob's public key), ... and the algorithm that Alice used for encryption. Trudy can thus mount ... . using the known standardized encryption algorithm and Bob's publicly available encryption key to encode any message she chooses. Trudy might well try to encode messages, or parts of messages she chooses. Trudy might well try, for example, to encode messages, or parts of messages, that she suspects that Alice might send.

Cleariy, if public key cryptography is to work, ... and encryption/decryption must be done in such a way that it is im­possible (or at least so hard to be impossible for all practical purposes) for an intruder to either determine Bob's private key somehow otherwise ... Alice's message to Bob. A second concern is that since Bob’s encryption key is public, …, including Alice or someone claiming to be Alice.

In the case of a single shared secret key, the fact that the sender knows the secret key ... . In the case of public key cryp­tography, however, this is no longer the case since anyone can Send an encrypted message to Bob using Bob's publicly avail­able key. Certificates, which we will study later, … .