  This article gives an elementary computational proof of the group law for
Edwards elliptic curves following Bernstein, Lange, et al., Edwards, and
Friedl. The associative law is expressed as a polynomial identity over the
integers that is directly checked by polynomial division. No preliminaries such
as intersection numbers, B\'ezout's theorem, projective geometry, divisors, or
Riemann Roch are required. The proofs have been designed to facilitate the
formal verification of elliptic curve cryptography.
