[joeyo]

The math-cannot-be-illegal argument gets more difficult when you consider that the digital representations of files are just really long numbers: Copyright infringement is making a copy of a (really secret) number. Possession of child pornography is the possession of a (really bad) number. etc.

I think the banning of encryption or forcing encryption products to have government backdoors would be horrifically bad policies, I don't think there is anything in our current legal framework that prevents it.