* Privacy

In privacy scenarios, there is a sender, a receiver and an attacker. For example, you want to send your credit-card to an online store. An attacker wants to capture the number. Your security here concerns itself with protecting the integrity and secrecy of a message in transit. It makes no attempt to restrict the disposition of your credit-card number after it is received by the store.

* Use-restriction

In DRM use-restriction scenarios, there is only a sender and an attacker, *who is also the intended recipient of the message*. I transmit a song to you so that you can listen to it, but try to stop you from copying it. This requires that your terminal obey my commands, even when you want it to obey *your* commands.

Understood this way, use-restriction and privacy are antithetical. As is often the case in security, increasing the security on one axis weakens the security on another. A terminal that is capable of being remotely controlled by a third party who is adversarial to its owner is a terminal that is capable of betraying its owner's privacy in numerous ways without the owner's consent or knowledge. A terminal that can *never* be used to override its owner's wishes is by definition a terminal that is better at protecting its owner's privacy.

posted by Cory Doctorow at 11:52:57 AM permalink | Other blogs' comments