I would like to encrypt my files for outside use (e.g. for Dropbox), but keep them unencrypted on my hard drive (for instance, to be accessible by indexing and other 3rd party software). Similar to TrueCrypt, though TrueCrypt does a slightly different thing: it mounts a virtual encrypted drive that sits in a file. The problem with that is, synching files in this mounted drive with Dropbox would lead to unencrypted Dropbox.
I am looking for an application similar to TrueCrypt that, for instance, mounts a virtual drive that mirrors an existing directory tree, except all encrypted files in it are now decrypted. Then I could sync the directory tree with Dropbox while using the mounted drive for 3rd party software. The synchronizing would involve either Windows 7 or Cygwin running under same.
Alternatively, I could manually keep two parallel directory structures: encrypted and unencrypted (though this would be an inferior approach); in this case, what's the most efficient way to synchronize them? I am talking about 20G of mostly PDF files and growing fast.
Or any other solution? Perhaps using Dropbox API?