iOS devices support
Please, add iOS support to give users the ability to decrypt files on their iOS devices.
Like on Dropbox, it would be nice to add the ability to designate a custom expiration time/date for a document(s). For example, 1 hour, 7 days, 1 month.
Number of Retries Feature
I just gave your application a try and it looks very interesting. Since you are writing the password hint to the file as it is encrypted, I wonder if you could add something like a 'number of retries' field where a person encrypting a file could set a limit on how many times the recipient could attempt to open the file?
Minimize to Menu Bar
It would be great to be able to minimize Encrypto to the menubar. Especially on Windows it would be nice to keep the desktop free of clutter while not needed, but always in reach if otherwise.
Add entry in contextual menu
It'd be great if the file or folder could be encrypted with Encrypto with just one right click, and call a service "Encrypt with Encrypto".
I know it can be made with Automator but Encrypto does not accept file or folder as workflow entry.