There is a very nice cryptography library for ActionScript 3 and it easily support the widest range of protocols ( TLS partial ), certificate( x.509 ), algorithms( RSA, AES, DES, 3DES, Blowfish, XTEA, RC4, ECB, CBC, CFB, CFB8, OFB, CTR ), and secure hashing ( MD, SHA ) I have seen to date.
AS3Crypto Library
I used SHA-1 extensively in IFBIN and will be using SHA-256 in IFBIN2 for managing data uniquely and install signatures. In looking at AS3Crypto it supports all I need for handling hashing on the client side.
I am a big fan of secure hashing as it has so many uses in writing software. Most think about hashing with regard to security but it has other useful features. A hashing algorithm takes some data input and produces unique output of a certain length. Say you wanted to store files on a server based on file contents so there are no duplicates, you could take a hash of the data you are going to store and use the hash as the file name. The higher levels of hashing (SHA256 and up) have very low odds of generating a duplicate hash so assigning keys this way is very handy.
Enjoy the AS3Crypto!
Cheers,
Ted :)
DIGG IT! 
Ted, are you referring to Hurlant's?
http://crypto.hurlant.com/
If so, I agree. This library is amazingly sweet. I have used it on a couple projects so far and love it. I vote for it to be added in the Flex SDK natively. :-)
I could not found the link. :)
It is friday and I forgot to post the link. All updated!
ted :)
Hey Ted, it looks like that Nike site is a good candidate for the new Module component! I noticed they called a new page for different topics...I assume it was to keep the main .swf small enough to load faster...etc.. However, the new module component in Flex3 would have eliminated the need for calling to a new page and been more seamless... :-)
Yet another advantage of Flex3