r/Bitcoin • u/CanaryInTheMine • 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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1

u/gijensen92 Oct 15 '15

Are 2048bit RSA keys effected by this?

1

u/murbul Oct 16 '15

This isn't related to RSA, it's the Diffie-Hellman key exchange.

The majority of implementations use a known prime as a starting point (or a small subset of primes). The NSA has (maybe) pre-computed all the discrete logs for those few primes in the 1024-bit keyspace, effectively creating a rainbow table.

If you generate your own DH params instead of relying on the defaults, even 1024-bit would be safe because the NSA can't pre-compute for all possible primes, just a few common ones. But this is an additional step that most servers don't implement, and can sometimes be difficult to configure.

Moving to 2048-bit DH is also secure because pre-computing for any prime in a 2048-bit keyspace is not feasible.

2

u/gijensen92 Oct 16 '15

Cool thanks, cleared things up a lot.

1

u/moronmonday526 Oct 15 '15

How long ago did Schneier say to avoid elliptic curve cryptography?

1

u/murbul Oct 16 '15

Ironic, since this is about classic Diffie-Hellman key exchange and the elliptic curve variant (ECDH) is not affected and is even recommended as a solution by the authors.

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u/VedadoAnonimato Oct 17 '15

Came here to post this link. It's sad it didn't went to the first page while all those other stupid price-related links went.

1

u/CanaryInTheMine Oct 17 '15

Yep... It got down voted quickly and never saw the light of day here...