The mathematics of information processing and the Internet can be organized around four fundamental themes: (1) access (finding information easily); (2) security (keeping information confidential); (3) accuracy (ensuring accurate information); and (4) efficiency (data compression). In this article, the author discusses each theme with reference to high school mathematics. He concludes with some recommendations for which topics within the mathematics of information processing deserve a place in the high school mathematics curriculum. (Contains 3 figures.)