Abstract of master's work

"Free space optic data-transmission lines with cryptographic protection"

Author: Dmitry Orlov

Theme: "Free space optic data-transmission lines with cryptographic protection"

Abstract

In this work the result is constructed module AOLS, which is not contain additional optics. It has been tested in short distance.

The system with only regular lens in the laser device and the photo diode without a focusing lens was used.

The given sample has successfully passed all stages of experimental check, and has shown ability of similar systems to be used in networks where it is not necessary to provide a highly reliability.

But it is possible to use for creation a point of the remote access to a network on rather small distances of data transmission - up to several hundreds meters.

We have to do the final choice of a computing element for cryptographic system, and development of fast algorithm of the enciphering focused on concrete hardware realization: the microcontroller, the microprocessor, etc.

Results of the researches which have been carried out in the given work can be used by development easy in manufacturing, simple in use, the cheap and protected device of the removed access to a network, capable to find application in an any local network, to provide satisfactory work at any specificity of use.

Goals, objectives, clues

• Realization of channel enciphering which is carried out "in hardware" more expensive, than enciphering in application layer, but last frequently cannot provide necessary speed of transfer. We should find compromise
• High cost of channel enciphering should not be aggravated with reduction of flexibility of use, there should be an opportunity of reconfiguration and reprogramming
• Reprogramming of system should not promote reception by the malefactor of access to the data or reprogramming of network
• Simultaneously enciphering on channel level and application level is much more expensive, but the greatest effect is observed only from introduction of both methods of enciphering
• Frequency of change of a key only minimizes consequences of breaking of the code, but does not reduce its probability
• We shall choose a class of enciphering code, to investigate expediency of application of block codes (high-speed and hardware-software oriented)
• Ciphers and decodes the same algorithm (they antisymmetric)
• Whether special measures are necessary for increase of protection, as well as reduction of redundancy
• The developed system should be investigated, being based on modern techniques of breaking on reliability and presence of weaknesses
• The size of the block is double word of the processor
• To provide satisfaction to the following requirements:
  • Construction of the code from simple transformations and alternation of polytypic operations
  • Cyclic iterative structure of algorithm
  • Antisymmetric structure of algorithm
  • Compactness of a code and the constant data 
• Maximization of usage of new approaches in construction of block codes with a confidential key, so-called fast codes. To compare application of universal codes to the codes focused on concrete hardware or program realization at functioning on systems with equal cost.

Current results

With the purpose of experimental check of an opportunity of creation of such systems, modeling has been carried out and on the basis of successful modeling the sample of the simplified system of the optical data link with use of inexpensive element base is collected experimental.

It has been realized FSO with the following characteristics:

1. Speed of transfer: 115 kByte/s
2. Capacity of a radiator: less 1mWt
3. A range: seen red
4. The interface from the COMPUTER: RS-232
5. Range of transfer: more than 130 m
6. Type of connection: simplex
7. A photo cell: photo diode FD-K-155
8. Laser (made in China, model of laser is not established)

Results of modeling of the receiver

The multivibrator generating a rectangular signal by frequency 57 kHz served in the second configuration as a source of a signal, the receiver was connected to a serial port of a personal computer and as a result the digital signal accepted through port by a computer was automatically estimated, and also was visually estimated a signal from an output of the receiver. The receiver and the transmitter have been fixed on external walls of two buildings, on distance of 130 meters. At absence of a straight sun ligtning the signal was accepted by the sun of the receiver, an atmospheric precipitation and a fog confidently, that is determined by a sufficient noise stability of the circuit by transfer on distance of 130 meters, and reception on the circuit the diode without additional optical system and diameter of a stain of the laser of 10 centimeters, capacity of the laser less than 1 milliwatt.

Now I am working on cheking productivity of "fast" block cryptoalgorithms.