I meant overwriting, not setting the file to zero length.
CCleaner has several methods of secure overwriting, none of which to my knowledge involve overwriting with zeros. The methods currently are:
Single pass - one pass of pseudo-random data
3-pass - Labelled as "DOD 5220.22-M", which is one pass each of zeros, ones, and pseudo-random data
7-pass - Labelled as NSA, but there is no specification I know for this, so I don't know what CCleaner is doing here, but given that none of the other ones end with a zeroizing pass, I doubt this one does either.
35-pass - Guttman, this is the unfortunate researcher that started the multi-pass overwrite craze. His method involves 4 passes of pseudo-random data, a whole bunch of passes that aim to mimic specific MFM patterns, then a final 4 passes of more pseudo-random data.
I am proposing that:
There be a single-pass overwrite-with-zeros method added A setting to add a final "zero" pass to the other methods, so you can still do a pass with pseudo-random data but end with zeros.
Multi-pass overwriting is not required. Guttman was tinfoil-hat paranoid back in the 90's when he wrote his paper, and the need for it has only diminished with increasing data densities. That's not my point, though. Let the paranoid people have multiple-pass overwriting. I just want to see the ability to overwrite with zeros because it makes things a whole lot easier in some cases.