[plt-scheme] What encryption libraries should we use with PLT Scheme?

What encryption libraries should we use with PLT Scheme?

I want to encrypt some data and write it to a file. Not sure whether I
should encrypt it first or encrypt the output port (or if that makes
sense to do so).

'encrypt' doesn't turn up any search results in the documentation or
in searching the google gruop so I assume there is nothing built in.

I found these libraries here that would probably work:

http://snow.iro.umontreal.ca/?tab=Packages