I have yet to use this part of openssl BUT on the command line this may/probly work.

openssl bf -in ./stuff_after_the_? -out ./decoded_info -d -k./key_here
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For figuiring out OpenSSL (because the Docs are alittle on the light side.) try openssl (command you want) asfd and it will print out a list of args for that openssl command. As for using the OpenSSL Modual. Sorry I can't help with that yet.