It uses binary zeroes. The last pass in a 35-pass write (according to CC's version of Gutmann) is also zeroes so the (apparent) end result is indeed the same. My opinion is that one pass is perfectly adequate anyway.
Out of interest, why do you think that random writes are better than zeroes?
It uses binary zeroes. The last pass in a 35-pass write (according to CC's version of Gutmann) is also zeroes so the (apparent) end result is indeed the same. My opinion is that one pass is perfectly adequate anyway.
Out of interest, why do you think that random writes are better than zeroes?
After a clean pass of 1's, the random writes just decrease the chances even more of anyone trying to recover data from it,
Note firstly "writing a series of 35 patterns over the region to be erased"
There may be a sequence of 0's in one pass, but 34 other passes will be different.
Secondly note that 1's and 0's are actually +value and -value.
The disc does NOT receive maximum magnetism for a sequence of 1's and zero magnetism for a sequence of 0's,
instead it receives a strong alternating magnetic field
and the 0's and 1' do NOT apply amplitude modulation,
but frequency or phase encoding, or something more esoteric.
If as you appear to suspect, a sequence of 0's was a sequence of nothings, then the data would NOT be self-clocking,
and then 1000 0's between a pair of 1's would become either 999 or 1001 given an error of 0.1% in the accuracy of time measurement or speed of rotation.
The Options/Settings/Wipe Free Space option uses one pass of binary zeroes (as does Secure Deletion of files one pass).
The Drive Wiper gives a choice of overwrite patterns, from one to 35 passes. I would assume that the one pass is binary zeroes. In the Gutmann 35-pass overwrite there are a series of different overwrite patterns, of which one is binary zeroes. The end result of a 35-pass overwrite with CC is zeroes, although this is pass number 10 (I think) in the obsolete Gutmann process.
Alan is of course correct, no data has ever been written directly to a disk, even in Gutmann's days. It is nowdays encoded many times so even if you could read the pattern on a disk it would be unintelligible. Actually bits aren't written to disk either, and a + doesn't indicate either a 1 or a 0 value, but that's another universe. What you see is what the disk controller has decoded and sent back to the O/S.