Adam Riese is a great mathematician, especially for modern algebra. IIUC, "nach Adam Riese" means "according to Adam Riese", which is used to express "(calculated) accurately with no doubt".

Werner Koch is, as you know, the principal developer of GnuPG, libgcrypt and its friends. It's up to us to admire his work using this expression. :-)

Possibly and likely, it would have already invented in German community.. I don't know.