[nsheridan]

This exists - http://man7.org/linux/man-pages/man1/ssh-keygen.1.html#CERTI... - though the tooling is a bit bare-bones. There are some tools written to use certificates though, such as Netflix's BLESS (https://github.com/Netflix/bless), Gravitational Teleport (https://github.com/gravitational/teleport) and my own (https://github.com/nsheridan/cashier)