> Rational fear of LN is a good thing, though. Minor splashes aren't bad, > but enough can cause serious burns.
You talk about what I call "respect". :) > I also worked with uranium in ceramics, though they were not > "uranium-based" (though sometimes we thought they were!). Black fragile thing looking like fine brick, weakly radioactive. Heavy fermion superconductor. Memories... :) > Sounds like you already have the gist. There are many good ways to pull > weak signals out of noise, either by direct integration over time or by > "chopper" techniques (e.g., only looking in narrow time intervals, via > gated integrators and boxcar averagers). I briefly seen such jamming generator, they are a real commercial product. I think it was sensing the computer's emissions, and altering the noise signal to counteract it. It surely wasn't a simple device. > And if the RF ID tag is sending out a signal over a couple of > different frequencies, using some pseudorandom sequence for the > frequency-hopping, then the "noise gain" can be enormous. That is, an > attacker trying to jam a spread-spectrum (Direct Sequence Spread > Spectrum, DSSS, typically) signal will have to match and greatly > exceed the frequences and times. True. How difficult is to detect the PRESENCE of such DSSS signal? > Even better, pulse systems which send out ultrawideband signals at > various coded time points (so-called Gold codes, or Kosami codes, for > example) are even more difficult to jam. Aren't they an annoying source of noise for everything non-spread-spectrum around? > already present. (And multiple detectors can help in various ways, much > the way noise-cancellation headphones work...off the shelf consumer > technology, so imagine what the spooks have.) I think I seen this approach even for receiving of weak TV signals. > Measuring leakage at a distance of a few centimeters is easy to do. How? Is there any cheap'n'easy way the interested part of the general public (thinking about people like on this List, not the Joe Sixpack cannon-fodder) could use? (Namely, is there some way how the detector device could be built by someone with not-too-many experiences with high frequencies?) > And if a leakage signal is very, very small at a few centimeters, the > usual inverse-square falloff will make it truly tiny at 100 meters or > so. (Where a van might be parked outside one's flat, for example.) Beware of the signals that spread along the power lines. > Truly sensitive communications may be best done on laptops, even > laptops in metal mesh bags. (Either with one's head poked into the bag, > or a bag big enough to enclose the user and laptop, etc.) ...or a big-enough well-grounded metal cabinet. Could additionally have the advantage of small, enclosed space that's easier to secure and audit than a typical room full of junk and books. Heard LCD screens radiate surprisingly strongly. See at http://www.eskimo.com/~joelm/tempestmisc.html > I would strongly bet on quietness of computers winning out over > increased RF detection capabilities. (Needless to say, detection goes > as the square of the antenna size, so even really large antennas don't > have that many dB of extra capture capability, compared to quietness at > the source.) RF is bitch. Spare tight all-metal enclosures, properly shielding a computer system is quite nontrivial. :( A simple RF radiation leakage detector would be a beneficial thing to have. If possible, it should be something a slight-above-average sysadmin would be able to handle. Hope you're right...
