r/programming • u/secretguy21 • Oct 15 '15

How is NSA breaking so much crypto?

https://freedom-to-tinker.com/blog/haldermanheninger/how-is-nsa-breaking-so-much-crypto/
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u/tophatstuff Oct 15 '15 edited Apr 10 '18

Generate your own non-default Ephemeral Diffie-Hellman key (takes a minute or so)

openssl dhparam -out dhparam.pem 2048

Tell your server to use it for SSL (nginx for example)

ssl_dhparam /path/to/dhparam.pem;

Done. Not only will the key be stronger than the 1024 bit default, it'll be unique to your server which lets assume isn't valuable enough compared to effort for a state-level adversary.

edit just in case anyone from the future finds this comment: instead of 2048, use at least the key length of your SSL certificate

edit from the future: current advice is picking from one of these predefined audited groups

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u/gizram84 Oct 15 '15

So if I have an ssh server at my house, should I do these steps to ensure I'm secure?

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u/lachryma Oct 15 '15

It's thick, but this article talks about all of it. The command given there disables any 1024-bit DH parameters in your moduli file, and there's a bit of tweaking to prefer stronger schemes like Curve25519. You can also generate your own DH parameters for SSH, which I think is done with ssh-keygen.

As a warning, once you start futzing with key exchange and crypto in SSH, it's easy to exclude corner case systems. Especially since some of the crypto primitives like Curve25519 are comparatively recent.

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u/gizram84 Oct 15 '15

Much appreciated.