Given a database of $N$ entries of which exactly one satisfies some
easily checked condition, classically it takes $O(N)$ trials to find the
satisfying entry. Grover's algorithm is a quantum algorithm which
reduces the work to $O(\sqrt{N})$ trials. One consequence is that in the
post-quantum regime, hash functions and symmetric ciphers only provide
half the security (measured as the log of the number of trials) as
currently provided. In this talk, we will give a brief description of
Grover's algorithm, including all of the necessary background in quantum
computing.