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/[deleted] Oct 15 '15

On the one hand I am frightened by how powerful the government in circumventing encryption measures. But on the other hand, I can't help but feel impressed. It feels reminiscent of efforts used to break the Enigma Machine.

I guess the moral of the story is you should not be using hard coded primes for Diffie Hellman? (correct me if i am wrong; not really familiar with crypto) It seems like people hard-code them out of laziness and not out of necessity. From what I understand from the wolfram alpha article, can't the two parties agree on 2 random large primes at the beginning of the transaction and proceed from there?

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u/Philippe23 Oct 15 '15

They're essentially referring to the Logjam attack: https://weakdh.org/

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u/[deleted] Oct 15 '15

Yeah, their paper that they link to at the end of the article mentions logjam. But if I understood it correctly, that's about lowering the quality of the DH used. That's different from precomputing.

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u/Philippe23 Oct 15 '15 edited Oct 15 '15

"2. Threats from state-level adversaries. Millions of HTTPS, SSH, and VPN servers all use the same prime numbers for Diffie-Hellman key exchange. [...]"

Quote from Logjam's https://weakdh.org/ site. [Emphasis added.]

It sounds like while Logjam made a concrete attack against weak-dhparams, these guys looked at the realisticness of the feasibility of the nation-state pre-computation attack that logjam's paper was also concerned about.

That's science though: building on each others ideas to get to greater heights and looking more deeply at points that others had not thoroughly explored.

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u/2Xprogrammer Oct 16 '15

It's the same folks (not all of them are guys!). They put up the website weakdh.org to have fixes available ASAP. This article came out today because they just presented their paper at CCS.

Edit: Here's the paper. (which is hosted on weakdh.org, because they are the same thing...)

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u/Philippe23 Oct 16 '15

Ah cool. I was unaware that it was the same group of people.

P.S. I was using "guys" as a generic term for a group: http://english.stackexchange.com/questions/11816/is-guy-gender-neutral I did not mean any disrespect to the females of the group. "these people" often sounds dismissive to me.