Besides MonkeyBread, you can also look at 360Works ScriptMaster 360works.com/scriptmaster/ whose example files contain encryption functions like AES, DES, etc.) ScriptMaster is based on 'Groovy' (which is a specific application of Java) which can incorporate external JAR modules to work. So, if you have JARs for PGP, you might be able use something you are already familiar with.
Troi also has Encryptor plug-in for FileMaker Pro 12 to 14 which can do AES-256 and several other integrations.
One thing that might prove difficult would be some version of single-sign on where the user manages to enter their PGP stuff on the machine in general and somehow FileMaker 'magically' knows they are authenticated and decrypts the data. But, if you can live with them authenticating within the FileMaker environment, then any of the suggestions should work.
-- Drew Tenenholz
P.S. ScriptMaster is FREE
Thank you guys, I will checkout the links/plugins.
Thanks a lot.