Schneier on Security

Clive Robinson • June 29, 2023 1:47 PM

@ ALL,

Ever wonder why it’s,called an X-Acto Knife?

It being the knife that put “cut”[1] in “Cut-n-Paste” for oh not far off of a century and still counting[2].

With X-Axto’s tag line of

X-ACTO Knives: Precision Cutting Tools, Hobby Knives, Office Supplies

You now know why the “Office Supplies” is more than just pencil sharpeners 😉

The fact is if you print documents in single sided form and physically cut out the words you want removed then the laws of physics will work for you not against you as it does with the ink in pens of all forms[3].

Or worse invisable to the eye meta-data in digital files. Whilst I’m known for advising,

“PAPER, Paper, Never DATA”

There is a bit more to “redacting than just printing it out.

[1] it comes as a surprise to some that for many years printing artwork was done by cutting things to fit and then get pasted into place on a carrying sheet[2]. Whilst scissors might be the choice that adults give children they are rarely sharp or precise enough. Thus the design of the X-Acto knife, with interchangable blades, originally thought up for surgeons but inappropriate due to being to difficult to clean and sterilize quickly gained use in the various forms of printing and publishing.

However there is a sort of lame joke about it being used by those wishing to remove words in the process of crime or censorship. That is there is a jurisprudence term “de facto” which in essence means,

“Acts/practices that happen/exist in reality.”

That is they are done often commonly irespective of if they are carried out by formal or officially recognized norms of law etc.

A capital X can not only be a shortening of “Ex” it is also used with hyphens to signify cut marks and similar. So saying X-facto whilst making a snipping scissors motion with the fingers was a way of saying someone had in effect cut away that which they did not want seen legally. But in a way that was not destroying evidence.

[2] Yes I still do this from time to time when producing doccuments as drafts. Where there are lots of figures and charts involved. I type up the text in an ordinary text-editor and put in the required spaces. Then drop in the figures charts and tables, and especially maths formula, that I’ve drawn up by hand, or lifted by photocopy from other sources.

[3] There are three basic types of computer printer, of which most people will only come across two,

1, Ink-Jet in their home printer.
2, Laser in their office printer.

Ink-jet printing uses a rapid dry liquid ink that is fired by rapid heating in a very tiny tube so a tiny drop of ink goes onto the paper and soaks into the paper chalk finish and paper fibers. When dry it makes the paper in those areas behave differently to subsequent applications of other inks.

Laser printers like photocopiers do not use ink, they use an incredibly fine plastic dust that gets transfered to the paper by a static electricity charge. It is then melted into place by a heated element. It is only a mechanical attachment to the surface of the paper and can be removed with solvent and heat so you can make your own T-Shirts etc. But it to obviously changes the surface of the paper to any other subsequent applications of inks.

So as the subsequent inks dry they form not just different thicknesses but surface texture, which by various “laws of nature” or physics can be made visable.

Clive Robinson • June 29, 2023 6:10 PM

@ Not Really…, ALL,

Re : Times change from Roman

“Proportional spacing of fonts provides more information than you might think about words cut out of the middle of text.”

Yes they do… Even when it’s just part of the “normal/default” font.

But some fonts have nearly non visable to the naked eye changes in the font for hiding meta-information and the like. Done quite deliberately as “Canary Traps” and the like.

In other words somebody is hiding information that can be used to trace not just the whole document but words within a document back to an individual print out…

It’s why I still use text editors on versions of non Microsoft DOS running on old versions of Unix running inside VM’s on more modern versions of *nix. Using printers that have non proportional fonts that you can check with a “projected mask”[1].

Not perfect and somewhat complicated but usually sufficient for just black ink/tonner printers. But… getting such printers is actually getting harder day by day these days, as HP in particular want to scam you via Ink/Tonner pricing tricks, which they put illegally –in Europe– inside their printer firmware along with serial numbers thus destroying peoples privacy.

[1] Depending on how old you are, you may or may not remember the old “over head projectors”(OHP) which you could put a printed page on and due to a bright light projeted down sufficient light was reflected back up then via a couple of lenses and a 45degree mirror onto a wall or reflective screen. Thus magnifing it upto to eleven times as big in both the horizontal and verticle (~10ft high in the verticle from a sheet of A4). So that any font changes can be checked likewise spacing etc. You would think such a simple OHP would be easy to keep going… nope you can not get the “projector bulbs” they need any longer, so you have to do some modifications with high power LEDs and switch mode power supplies…