mccartney@io.dec.com (James T. McCartney III - DTN 381-2244 ZK02-3R54) (11/04/87)
> I am interested in 'Why' 100 alternate 1/0 writes will not declassify some > media. It seems to me that after 5 or so random 1/0 writes the original > data would be so far gone that retreival by any means is impossible. The reasons for this are known and are specified in the TEMPEST regulations which describe how classified electonic and magnetic media must be handled. This document is also classified, thus it can't be discussed in an open forum. If you are interested and have a need to know, contact you installation security officer and they can provide details.
aglew@ccvaxa.UUCP (11/07/87)
..> Declassifying electronic media Writing alnernating bands of zeroes and ones a few times might be a good start. 101010... 11001100... 1111000011110000.... Next, one would want to write a random bit pattern over the data you want to declassify. But even then you have to worry about jitter, about the analog bit patterns not quite matching up with the original when overwriting. Plus effects that might come from the tape running a bit slower/faster...