Hi all,
In my opinion, the password entry dialog is not usable for long phrases, and encourages poor passwords. A checkbox to render the contents visible would be very useful to catch typing mistakes. It is frustrating to be told five times that the two do not match. Not everyone can touch type a long sentence twice with no mistakes.
The security in concealing password entry is dubious anyway. It has value for protecting authentication passwords in places where someone may be looking over your shoulder. But would you be working with a highly sensitive document (that is worth protecting with AES) in such an environment? Its contents are as secret as the password used to protect it, and so it makes no sense to conceal the password from prying eyes, yet reveal the document.
Another issue with the Windows application is that it performs sanity checks in the wrong order. When you're encrypting or decrypting a document, first you must get through the password dialog. Only then are you told, oops, the destination file already exists and we must bail! There is no security benefit in this; it is just annoying behavior. Why ask for the password if the operation cannot possibly complete (unless someone deletes the file outside of the program). Just bail right away: "We cannot do this operation because the destination file exists."
A useful behavior would be to have the option to rename the existing file, or to choose a different name for the newly created file. (Deletion should be deferred to the user, who should be using a secure shred program, at least for the plaintexts).
Cheers ...