I was reading https://weakdh.org/sysadmin.html
They also have a very interesting paper as a PDF.
Anyway it appears that most ssh servers, when using DHE key exchange, use the 1024-bit Oakley Group 2 and there is suspicion the NSA has done the pre-computations needed to passively decrypt any tls communication using DHE with that particular prime group.
They recommend setting the following:
KexAlgorithms curve25519-sha256@libssh.org
I don't even see that directive in my sshd config to set it, I suppose it may be one that is manually added when needed but I want to verify it actually means something in CentOS 7 ssh.
Also I'm a little worried that maybe curve25519 is one of the curves that Red Hat (and thus CentOS 7) doesn't support due to patent concerns.
If it is, is there a suggestion on what curve should be used instead?