1.8. Why do I need a lot of different shifrmashin Because there is no single, suitable for all cases the method of data encryption. Selecting cryptographic system depends on the characteristics of the information, its values ??and the owners ability to protect its information. First of all, we emphasize a great variety of species of protected information: documentary, telephone, television, computer, etc. Each type of information has its own specific characteristics, and these characteristics strongly influence the choice of encryption methods. Of great importance are the volume and the required encrypted data transmission speed. Selecting the type of cipher, its parameters and its resistance depends strongly on the nature of the protected secrets or mysteries. Some secrets (. Eg, government, military, etc.) must be kept for decades, and some (such as stock) - within a few hours you can disclose. It should also take into account the possibility of the enemy, from which this information is protected. It is one thing - to withstand the single or even a gang of criminals, and another powerful state structure.