What I want is about this: Files are encrypted on the server, apache can decrypt it with certificates the client has to have installed and then send it encrypted to the client via SSL.
So the files are always encrypted on the server (except the moment apache decrypts it to encrypt it again).
Another possibility would be to have something like an TrueCrypt-Server. However, each client must have write access, just like they would with a ftp server.
Does anyone know such a server-program.