encrypted file system or folder

[Bart Silverstrim]

Tomoki Taniguchi wrote:
> I don't know if such a solution exists,
> but I am looking for an encrypted filesystem/folder
> solution which meet the following requirements
> or comes close to meeting them.
> 
> 1) accessible by both windows and linux
> 2) folder based rather than a full filesystem.
> 3) encryption is based on a "key" file
> 4) access to the encrypted folder is transparent once opened with key file
> 
> the following are features that i would like to have, but image pretty
> hard to implement
> 1) can setup read-only encrypted folders
> 2) can differentiate access between read-only and read-write based on
> different key files.
> 3) or an ACL based encrypted folder.  differentiating access levels
> based on user name, id , or user specific key file.

Would Truecrypt fit the bill?  You should be able to google it for the 
home page...