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Слово

Перевод

Предложение

to compromise

подвергать риску, компрометировать

Encryption techniques can be classified broadly according to how much of the encryption process need be keot secret in order not to comDromise encrvoted texts.

to require

приказывать, требовать, нуждаться в чем-либо

In the following sections of this chapter we consider three categories of methods that require protection for respectively.

to consider

рассматривать, обсуждать, полагать

respectively

соответственно, в указанном порядке

knowledge

знание

Our first category of methods requires that the encryption algorithm itself be kept secret (private) because knowledge of the encryption algorithm is sufficient to produce a decryption algorithm.

sufficient

достаточный,

достаточное

количество

to describe

описывать,

характеризовать

An algorithm typically does not use a key as described above.

sequence

последовательность, ряд,порядок

For example, encryption may consist of a sequence of reversible steps.

to reverse

поворачивать(ся) в противоположном направлении, перевертывать

Слово

Перевод

Предложение

to apply

применять

If the steps were known, the inverse operations could simply be applied in the reverse order to decrypt a ciphertext.

to compress

сжимать

Compress the file using Huffman ceding.

to swap

менять, обмениваться

Swap disjoint pairs of bytes.

lo allow

позволять, разрешать

Knowledge of the algorithm may allow a more focused attack on a ciphertext but is not by itself sufficient.

arbitrary

произвольный;,

капризный,

деспотический

An arbitrary ciphertext file is protected by keeping secret the key needed to decrypt it.

feasible

выполнимый,

осуществимый,

вероятный

It should not be feasible for an attacker to decrypt a ciphertext via a direct search of the key space.

lo replace

вернуть, восстановить, заменить

To encrvDt a file, replace each character bv the

lo wrap

завертывать,

сворачивать,

заворачивать

character k further on in the (wrap-around) alphabet.

row

ряд

Suppose we write out the alphabet, as in the top row for example, and make the bottom row a permutation of it.

lo map

наносить, накладывать

If we map out alphabet onto the integers 0 to 52 and perform modulo 52 addition on a pair of characters, the ciphertext resulting from our example can be represented.

Слово

Перевод

Предложение

equal

равный, одинаковый

We saw in the previous chapter that natural language is redundant- letters and letter groups do not occur with equal frequencies.

clue

ключ, улика, нить

If the text is large enough, the frequency distribution of the characters in the ciphertext gives clues as to their identity in the plaintext.

to deduce

выводить заключение, проследить

Even in the shot example above we might deduce that a space is represented by R because of the frequency and spacing of that character.

frequency

частота

to avoid

избегать

We can avoid the one-to- one correspondence between characters in the plaintext and characters in the encrypted text by merging the plaintext in some way with (repetitions of a keyword.

to merge

поглощать,

сливать(ся),

соединять(ся)

vulnerable

уязвимый, ранимый

However, repeating patterns make the ciphertext more vulnerable than if an arbitrary 42-character keyword had been used.