Tag Archives: ecc

ECC, NSA and Crypto Agility

Matthew Green, someone I admire, recently did a wonderful post on the NSA announcement deprecating secp256r1 and letting people know they are no longer encouraging further adoption of the Suite B.

As always Mr. Green has put together a well researched article that is a joy to read. I won’t rehash it more than necessary, but I think he missed an angle that deserves some discussion.

Over the last decade (Suite B is over 10 years old) we have seen more improvements in cryptanalysis than you can shake a stick at. This, as his post points out, is important since ECC doesn’t offer much of a margin for error.

“But while the ability to use (relatively) tiny elliptic curve points is wonderful for implementers, it leaves no room for error. If NSA’s mathematicians began to make even modest, but sustained advances in the state of the art for solving the ECDLP, it would put the entire field at risk. Beginning with the smallest of the standard curves, P-256, which would now provide less than the required 128-bit security.”

With hindsight, we can probably say those who advocated its adoption did not fully appreciate this, or how easy and cheap it it is today to get access to massive amounts computing power.

“Did I mention that as part of the recent announcement, NSA also deprecated P-256?”

If I were a betting man, I would say this is why they have deprecated P-256, not due to some conspiracy theory, instead consider, maybe they are simply playing it safe?

But why then stop encouraging the adoption of Suite B all together? I think the answer to this lays, not in some secret knowledge about advancements in quantum computing, but instead is rooted in the reality that after a decade of pushing ECC it’s still seldom used (when compared to RSA).

If the NSA were to spend the next decade pushing Suite B (or more at the current adoption rates)  they will have spent tons (of the governments and others) of money along with their credibility. This would also be a more difficult task given the IETFs push for Curve25519. All of which would just be thrown out once they pick their “winner” for a quantum computing resistant algorithm.

The reality is getting the world to upgrade its crypto is hard and takes time. Operating systems applications and protocols are simply not designed for it. Additionally, with the way things are designed today it works out to be mostly an all or nothing process. Just look at how difficult the relatively simple  deprecation of SHA1 has been.

I am often the the one who says “You’re not paranoid if they really are out to get you” but in this case I think we’re likely looking at the NSA’s version of pragmatism and not a nefarious plan.

On the other hand, as a friend pointed out this could be a way for them to derail Curve25519, either maliciously or benevolently.

Using ECC keys in X509 certificates

Recently the CAB Forum published a document called the Baseline Requirements for the Issuance and Management of Publicly Trusted Certificates.

This document was authored by both browsers and public CAs and is used by the browser vendors to mandate what minimum technical requirements need to be met for inclusion into their “Root Programs”.

One of the changes specified in this document is that subscriber certificates (aka SSL certificates) containing RSA keys must have a bit length of 2048. This is a change for a lot of CAs (GlobalSign had made this change some time ago) one that has implications to server operators.

Just take a look at the Crypto Plus Plus Benchmarks to see how much more expensive 2048 bit RSA. For most users this additional computational cost won’t be an issue but in some cases customers may need to increase the computing power they allocate for SSL establishment.

But what alternatives do you have? Well there is one, certificates with ECC keys; using these have the potential to significantly decrease the computational costs for SSL negotiations (even over your old 1024bit RSA certificate) but they come at a significant penalty – compatibility.

ECC was not supported in Windows until VISTA which was released in 2009, this basically means 100% of the XP clients out there (around 29% of the browsers on the internet as of July 2012) would be unable to establish a session with your website if you switched exclusively to ECC.

This is important for more than just Internet Explorer users since even Chrome and Safari use CryptoAPI for certificate validation when on Windows.

This would mean these users would see something like this:


That is pretty scary, so how long until we can use this more broadly? It’s hard to say there is a good article titled “The developers guide to browser adoption rates” that sheds some light, that and the historic gs.statcounter.com results. Based on these unless there is a sudden change (which is possible these machines are getting pretty old) I would assume that we have around 4-5 years of XP out there yet.

Hope this helps,