Virtually all server side hardware can do AES-NI instructions in hardware now (unless you are using ATOM cpu for ssl connections?) and most non-mobile hardware clients can do AESNI too for AES-128
The problem with AES isn't performance. Sites have been using AES ciphersuites in TLS for many years.
The problem is that the widely-deployed AES ciphersuite, like the ciphersuites for triple DES and IDEA, uses a construction from the '90s that is itself insecure. It's based on CBC mode (which is fine) in a MAC-then-encrypt configuration (which is not), which lead to the Lucky 13 attack, and which until TLS 1.1 didn't properly set up the IVs for each record, which lead to BEAST.
No major site used RC4 because it was more performant. They used it as a workaround to Lucky 13 and BEAST, because they couldn't count on browsers fixing those problems fast enough.
So as a sort-of-amusing counterpoint to this article, I know at least one ASV who insists that the only way to mitigate BEAST is to disable all ciphers but RC4. Still scratching my head on that one.
That tool you posted is great, hugely helpful for anyone who has to deal with this stuff.
Yes, I know, but it seems a little bit misguided / misleading, particularly since the BEAST in particular was pretty much mitigated in most browsers (see the link I posted + other links I posted below).
(The idea behind the config above is to propose TLS 1.2 ciphersuites, which aren't susceptible to BEAST, and leave RC4 as a fallback for older TLS implementations. But TLS 1.2 support in browsers is still problematic.)
Also, ECDHE-RSA-AES128-SHA256 is still decrypt-then-verify CBC mode, isn't it? GCM should be listed first.
A lot of sites are on hardware that's older than two years old (AES-NI didn't show up till Westmere), or an OS that's more than two years old (Ubuntu Lucid, for example, ships with OpenSSL 0.9.8).
I would love it if Atom gets AES-NI as most consumer/smb NAS devices us that CPU and it would mean that we could finally have essentially wire speed encryption for those devices.
http://dl.dropbox.com/u/24257718/cipher_chart.png
Virtually all server side hardware can do AES-NI instructions in hardware now (unless you are using ATOM cpu for ssl connections?) and most non-mobile hardware clients can do AESNI too for AES-128