From where are you sending the flat file?
What is the planned processing once the file is in TN? Unless the plan is to process the data as an opaque item (not looking in it for anything) then it will need to be unencrypted.
Can you provide additional details of the planned steps and components?
If you have not read the wM docs covering TN usage, please do so.
#Integration-Server-and-ESB#B2B-Integration#webMethods