Encryption, built in class?

I want to write a document class to be run within Flash on another computer. I would have the encrypted message in the code and when the class is run it returns the decrypted message.

I can see there’re many 3rd party libraries around. However without assuming the other person has the same library installed, has flash got an encryption class (or similar) built in? Or I’ll have to write the encryption myself? Any ideas?

Thanks for your help.