Saving user credentials in a Silverlight application

Question

What is the best way of saving user credentials in a Silverlight application?

We're making use of the new Silverlight 3 feature that allows WCF calls to be authenticated: we prompt the user for their credentials to the service within Silverlight, and we want to offer a "remember my password" feature.

In .Net we can use the ProtectedData class, but it appears that there is no Silverlight version of this available.

Answer 1

We're saving credentials to isolated storage and using the System.Security.Cryptography.AesManaged class to encrypt them. This is hackable - if someone got on your users computer and had already compromised the user's network/Windows login they could read the isolated storage file & pull the keys from your .xap to decrypt the data. For our purposes that's an acceptable risk.