Lost cost countermeasures against compromising electromagnetic computer emanations
US6721423B1 · kind B1 · utility
Inventors
Key dates
| Filing date | Jan 28, 1999 |
| Grant date | Apr 13, 2004 |
| Priority date | — |
| Expiry date | Jan 28, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F21/84
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A set of methods is specified whereby software reduces compromising electromagnetic emanations of computers that could otherwise allow eavesdroppers to reconstruct sensitive processed data using periodic averaging techniques. Fonts for screen display of text are low-pass filtered to attenuate those spectral components that radiate most strongly, without significantly affecting the readability of the text, while the character glyphs displayed are chosen at random from sets that are visually equivalent but that radiate differently. Keyboard microcontroller scan loops are also furnished with random variations that hinder reconstruction of the signal emanated by a keyboard. Drivers for hard disks and other mass-storage devices ensure that the read head is never parked over confidential data longer than necessary.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.