Protection of computers from side electromagnetic radiation during monitor images formation

Abstract

Reliable protection of confidential data processed in critical information infrastructure elements of public institutions and
private organizations is topical task today. Of particular interest are methods to prevent the leakage of confidential data by localizing
informative (dangerous) signals that both carry an informative component, and have a signal level higher than predefined threshold.
The increase in signal energy from personal computers is caused by increasing of its transistors switching speed. Modern passive
shielding methods for secured computers, similar to the well-known program TEMPEST, require either costly and large shielding
units or technological simplification by using of low-cost fragmentary shielding of computer’s individual elements. Therefore,
localization of side electromagnetic radiation produced by personal computer is needed. The paper presents a cost-effective approach
to reducing the level of computer’s electromagnetic radiation by passive method. The radiation are localized and measured by its
estimation on personal computer’s elements, namely unshielded communication lines between video processor and a monitor,
fragments of electric tracks on motherboards, etc. During experiments authors used ad-hoc miniature electric (ball antenna) and
magnetic (Hall sensor) antennas connected to selective voltmeters. This approach significantly reduces the cost of equipment and
measurements as well as requirements to analytics’ qualification for improving computer’s protection. Also, the alternative approach
for computer protection is proposed. The approach is based on image content protection by distorting the image on the monitor
instead of reducing electromagnetic radiation caused by signals from the monitor. The protection includes image scrambling using
Arnold transform that randomly “shuffle” the lines in each frame.