Expander graphs are sparse but highly connected graphs, which find a variety of uses in CS. If the vertices of an expander are labelled by 0 or 1, a $t$-step walk gives a $t$-bit string.

Cryptography is a beautiful branch of theoretical computer science that seeks to provide guarantees to the art of secret keeping. The questions it poses are fundamental --  does the universe permit asymmetry of computation?

In 1948, Claude Shannon wrote his landmark paper on "A mathematical theory of communication", which paved way to the field of information theory.

A Boolean function f on n variables is called a polymorphism of another Boolean function g on m variables if their operations commute.