Yes, even here, encrypted broadcasts are possible. But there is no smartcard slot on the receiver, so how does it all work?

The encryption used is Worldspace's own standard, proprietary system, and thereby commercially secret, so I'll describe the facts as I know them and try to guess a little extra.

Firstly every Worldspace receiver has an identity number. There is plenty of scope for this number to be unique, as the identity number is 16 digits long!

To be able to decrypt an encrypted broadcast the new subscriber sends his subscription fee and his receiver's 16-digit identity number to the broadcaster in question. The subscriber gets sent, in return, a password which is 22 digits long! This password is keyed into the receiver. Luckily there is an opportunity to edit the password after entry, because the possibility of miskeying it must be pretty high.

This form of decryption mainly relies upon obscurity for its efficacy. It is unlikely that users would continue to type in different 22 digit numbers, until they eventually found the magic password that unlocked the service, because it is much more likely that the sun and all the stars would go out first.

The weakest point of the system, from a hackers point of view, is the embedded 16 digit identity number in the receiver, because once you can reprogram the receiver's identity code you can make thousands of 'cloned' receivers that can all share the same password.

There are, of course, other ways to break the system, any good book on cryptography would give you a head start here.

The weakest point of the system from Worldspace's point of view is that the receiver can only store one password, and this might mean that only one service can be subscribed to.