It is now possible and recommended to log into Ocean Grid securely using TLS (often wrongly known by the name of its now defunct predecessor SSL). The OpenSim software does not directly allow this, although simulators can communicate with the ROBUST server and the viewer by secure ports (for example the 1280x1280 test region Rheged on Ocean Grid). However, it is possibly to achieve secure logins using a reverse proxy like Nginx, which is what was used here. The port that has been used is 9002. The information on the web site has been updated accordingly. The insecure port 8002 is still available for the reasons explained below. Both work fine. Please use the secure port if you can.
A blog post detailing how this was done can now be found will appear on Starflower Bracken's blog in the fullness of time. We have used Let's Encrypt certificates and these are accepted by the viewer. If you get an SSL connect error, please read the next paragraph because it DOES work and it's not a problem with the grid:
Issue: there is a viewer bug [FIRE-24068, SV-2392] in all older viewers that prevents the Grid selector from allowing https:// prefixes, which is annoying. This means, for the present if you use such viewers, that you may need to manually edit grids.user.xml or grids.xml depending on which viewer you use. Consequently this isn't yet very accessible except to users of older viewers with unless they have considerable technical competence. For now, This means that the old insecure HTTP port 8002 will remain in use as well but this is now under review.
[Edited: 2020-05-03, 2021-09-26]