Tasks are decided by cryptographic methods

When speech goes about cryptographic protection, an accent is done on cryptographic algorithms.

All of difficult cryptosystems are built on the base of the simplest transformations:

- replacements;

- transpositions;

- functional transformations.

The cryptographic methods of protection are intended for protection of processes of informative co-operation from a rejection them from the normal flow of process and from the purposeful actions of disturber.

Informative co-operation is co-operation of a few legal participants, basic maintenance of which is an exchange by information between them.

The normal flowing of process of informative co-operation is meant by accordance of process to the parameters of its flowing, to planned by person which tries to execute a standing task before him. Any events, destroying this process for scopes a norm, are rejections.

Types and classification of ciphers

Classification of ciphers is presented on a picture 2.

Picture 2 - Classification of ciphers

Pointers on a picture mean the most meaningful subclasses of ciphers. The dotted lines mean that ciphers can be examined and as a block, and as ciphers of replacement.

Symmetric ciphers utillize the same key for encryption and decryption.

Asymmetrical ciphers are utillized the different keys.

In line ciphers every character is ciphered on a separateness.

At the use of block ciphers, a plaintext is divided by the blocks of the fixed length, each of which is ciphered on a separateness. A size of block to date is 64, 128 or 256 bit.

The ciphers of gamming form the subclass of multialphabetical ciphers. They behave to line ciphers and they are symmetric.