Shredders used to use a simple method – they cut the paper into very thin lines, that were
totally unreadable.
Or, at least,
so everybody thought. After the takeover of the American embassy in
Teheran (something like 1972?),
Iran’s new security forces just gave enough people enough time, and results were achieved. Many
CIA and
state-department documents were recombined, often causing embarrassment as Iranians told different countries in the world what the US
really thought about them.
Since that day, shredders cut the paper into really tiny small square thingies.