We are using SSL encryption to connect via VPN to a vendor using a TCP/IP sockets connection. It’s been rock solid for a few years now. I used a third party SSL package to generate my keys, got the SSL license from Quovadx, then configured the thread with the location of the license key files and voila!
We also have one interface that we use a file encryption on. A state institution that we work with uses PGP encryption – basically they gave us an encoding phrase to encrypt/decrpyt files that we ftp to/from them. With a bit of scripting, I automated this process of stopping the thread that creates the file, run a tcl script to create file headers/trailers, encrypt the file with their PGP phrase, and ftp the file to them. We are on AIX as well.