During the guarantee of safety of the information of the service lives of personal computers much depends of selection of the methods of the protection of information on the floppy disks (diskettes) from the unsanctioned copying.

The authors of this article besides a classical change in the structure diskettes (tyings to the time parameters of reading and record, nonstandard marking of paths and change in the distance) propose to use methods of coding the information, which is stored on the flexible disk, in accordance with the algorithm of cryptographic conversion according to GOST 28147-89 in the regime of with the feedback.

The algorithm of cryptographic conversion is intended for the apparatus or program realization, he satisfies cryptographic requirements, but his possibilities do not set limitations on the application.

For the more clear understanding of the essence of the method of the protection of information on the floppy disks from the copying let us examine differences in the standard structure diskettes and the structure, realized in this method.

On the standard diskette after formatting it is possible to isolate four basic regions, namely: loading sector (boot area), region the table of arrangement are file (FAT area), root catalog (directory area) and the region of data (data area). Loading sector is always the first sector on the diskette, precisely, here is written information about how it is organized diskette. Due to this operating system makes it possible to work with the large collection of the differently organized flexible disks.

The designation of some it is byte the loading sector, which describe organization diskettes, they are given below:

11-12 bytes - the number it is byte in the sector;

13 bytes - number of sectors in the cluster;

14-15 bytes - number of reserve sectors;

16 bytes - number of copies FAT;

17-18 bytes - number of positions in the root catalog;

19-20 bytes - number of sectors on the disk;

21 bytes - code of the type of disk.

The following area of importance - FAT, in which operating system assigns sectors for positioning different it is file. Here for each sector there is its record, which contains information about that, sector is occupied with file or not, if yes, then by what precisely, and is also indicated information about the damaged sectors.

The size of the table of arrangement is file it depends on the size of the disk: the higher its capacity, the greater the size must be in the table for storing the information about all sectors of disk. For the larger reliability of similar tables there can be several (usually for the standard diskettes 3,5 "with the capacity of 1,44 mb. their two).

In the root catalog the information about the files, the catalogs, the time and the date of their creation, the sizes and other necessary information is stored. Of each position of catalog are removed 32 bytes, whose designation is given below:

1-8 - name of file;

9 - 11 bytes - expansion of name;

12 bytes - attributes of file;

13-22 bytes - in the reserve of operating system;

23-24 bytes - time of creation;

25-26 bytes - date of creation;

27-28 bytes - initial cluster;

29-32 bytes - size of the file.

All the remaining disk space is the region of data, in which is stored the information.

The use of a method of the protection of information on the floppy disks from the copying implies the creation of structure diskettes, by different from the standard.

With the formatting the diskettes are created the following divisions: system region and the region of data. In the system region dimension of file in the bytes, its name and expansion, password, with which this file was encoded, information about the order of the arrangement of sectors and the damaged sectors. System region and region with the data are stored in the encoded form.

On the standard diskettes DOS with the record it is file is formed the table of their arrangement, in which is indicated the sequence of the arrangement of sectors for each file. The application of a classical method of changing the parameters of disk drive suppresses the possibility of survey diskettes by conventional means, which work with the standard sizes diskette, as a result of which similar to diskette cannot be copied without the specific routines.

Using program DISK EXPLORER, it is possible to analyze logical structure diskettes and, after reading each sector, to make separate copies of sectors, which are located on the diskette) after a change in the parameters of disk drive. But obtaining the total volume of information in this case is impossible, since the sequence of the arrangement of sectors with the data to user is not known, but the determination of necessary sequence will require the sorting of many combinations.

In order to change the regime of the work of disk drive, it is necessary to modify contents specific storage cells. Through address 0000h:0078h is located the indication of the table of data, which are used by a controller of disk drive with the work with diskette, and a change in these parameters will make it possible to work with the nonstandard sizes diskette.

In this method the formatting with the parameters, which are differed for each sector, is used. Two sectors are used for storing the system information (size, the complete name of file, the data about the sequence of sectors and the damaged sectors, the password, with which it was encoded file).

During the formatting the quality of record and readout of sector is checked, since the permissible volume can change because of the potential presence on the diskette of the damaged sectors on it. After this, is calculated free volume on the disk and it is compared with the size of the written file.

During the restoration of file in user inquires the password, by means of which system region is decoded and is checked the password, obtained in the process of decoding. The work completes with the no coincidence. In the case of positive result the new parameters for the disk drive are advanced, and occurs the decoding of the file, recorded to the disk.

Is the major advantage of the developed method the high cryptographic durability of the information, written to the floppy disk, which is reached because of the application of an algorithm of the cryptographic conversion, based on guest 28147-89.

On the basis of the described method was developed and fixed software, which realizes its work in practice, into which enter the programs of the record of information to disk and readings of information from the disk.

In comparison with the existing standard programs for the personal computers the speed of reading and writing is reduced in them by 10 %