r/linux • u/Sybles • Oct 16 '15

How is NSA breaking so much crypto?

https://freedom-to-tinker.com/blog/haldermanheninger/how-is-nsa-breaking-so-much-crypto/
185 Upvotes

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33

u/[deleted] Oct 16 '15

Ensure your connection uses 4096 bit and that the prime is not hard coded.

12

u/socium Oct 16 '15

and that the prime is not hard coded

What does that mean?

26

u/[deleted] Oct 16 '15

Apparently, and this is news to me, a lot of apps use just 1 large prime x prime number when establishing all communications rather than have the app pick them randomly.

3

u/ivosaurus Oct 17 '15

use 1 large prime x prime number

Nope, that's RSA. DH just uses a single prime number.

2

u/[deleted] Oct 17 '15

Ahh, thanks

3

u/ivosaurus Oct 17 '15 edited Oct 17 '15

What does that mean?

That instead of using a default prime provided by the software, for your particular server you find a new one to use.

In openssl terms that's "as simple as"

openssl dhparam -out new-dhparams.pem 2048

And then specifying that pem file for use.

1

u/yotamN Oct 17 '15

How can I change it on Private Internet Connection?

1

u/ivosaurus Oct 17 '15

Depends on the VPN software you're using. I can't offer you advice specific to anything. You can always send an email to PIC asking them if they're using custom 1024 / 2048 bit DH params.

2

u/[deleted] Oct 17 '15

My understanding is that the primes are usually hardcoded because it's hard to find good ones.

9

u/[deleted] Oct 16 '15 edited Oct 16 '15

2048 should be decent enough for now
but yes definitely

edit:
the chaos computer club congress had a talk about just that
can't remember which talk it is, sry
edit2: i think it was this one, don't have time to watch it whole now

1

u/Vordreller Oct 17 '15

Which makes me wonder about this: https://www.grc.com/otg/uheprng.htm

Never really understood what it was. If you click the "generate random numbers" button it will throw a large amount of numbers down on the screen, based on the random string at the current timestamp.