A gem from Hacker News

gistfile1.txt

Source: https://news.ycombinator.com/item?id=13198567

Always, always, always generate your own SSH moduli.
reply
	
notyourwork 4 hours ago [-]

For those uninformed you should expand on this to. It is a great suggestion but a statement like this to a uninformed isn't very helpful.
reply
	
poisonarena 4 hours ago [-]

please elaborate!
reply
	
knweiss 1 hour ago [-]

From the OpenSSH moduli(5) man page:
  "When performing Diffie-Hellman Group Exchange, sshd(8)
  first estimates the size of the modulus required to
  produce enough Diffie-Hellman output to sufficiently
  key the selected symmetric cipher. sshd(8) then randomly
  selects a modulus from /etc/ssh/moduli that best meets
  the size requirement."
The problem is
a) OS distributions ship pre-computed moduli in the /etc/ssh/moduli file. I.e. most users don't change these moduli. This facilitates pre-computation attacks.
b) These moduli are often too short (<2048 bit).
You can create your own moduli with ssh-keygen (see the "MODULI GENERATION" section in the ssh-keygen manpage).
FWIW: Here's my open bug for RHEL7 where I try to convince Red Hat to improve the situation (including more details and references):
https://bugzilla.redhat.com/show_bug.cgi?id=1396943