Symptom: ssh login to the DSOC/NMASC login machine (= login.aoc.nrao.edu, ssh.aoc.nrao.edu, or gygax.aoc.nrao.edu) fails with "Bad server host key: Invalid key length"
Cause: Your machine no longer trusts the oldest host key on the NRAO server, and rejects the connection instead of switching to one of the newer host keys being offered.
Solution: edit your .ssh/config file on your local machine:
In a terminal:
1. cd ~/.ssh
2. ls to see if you have a config file already. If you have a config file already, continue to setp 4.
3. Create a text file called "config" using your preferred text editor
4. Edit your config file to add the following:
Host gygax.aoc.nrao.edu login.aoc.nrao.edu ssh.aoc.nrao.edu
5. Save your edit.
This should solve your login issues: if not, please submit a new helpdesk ticket.