I have a client who is in need of a file based encryption / decryption application to be used between Linux / Windows 2003 Server. The goal is to have a single file compressed nightly on a linux platform and secured using a script, transmitted over FTP, decrypted on the Windows 2003 server and available for other import routines such as SSIS, etc.
The file can remain unencrypted on each end after transport, the desire is mainly to keep the file secure during transport. Firewall rules and the fact that IIS6 doesn’t support SFTP eliminate SFTP as an option. Simplicity is the primary focus here, so complex security options or heavyweight libraries cannot be used.
You could try GnuPG, it’s cross platform and since you are only sending files internally you don’t really need a certificate signed by a big-name certificate authority.