I have no firsthand knowledge, but a friend who was into this a few years ago told me that the following is used for NSA's "best stuff" on paper... First, it is shredded. Then, it is burned. Then, the ashes are soaked in acid Then the acid is allowed to evaporate and the resulting mass is formed into bricks. The bricks are dumped at sea at a classified location which is changed weekly. Maybe he was putting me on, but... A few years ago, the American embassy in (I think) Teheran was invaded by mobs of locals. They apparently managed to get hold of a lot of classified documents which had been shredded in the minutes before they managed to break in. But a few months later, there appeared in the New York Times reconstructions of a few pages of the original material, based on a lot of tedious labor. So, maybe the procedures above aren't excessive...