Notation

We give informal definitions of our notation; this gives us a convenient shorthand for discussing security properties.

A B

This expression means that any protection mechanisms provided by a smart card with B can also be provided by a smart card with A. For example, ``trusted input no input'' because a smart card that has no input can be simulated by a smart card that does have trusted input.

A B

This expression means that both A B and B A.

A+B

This expression refers to a class of communication security properties provided by smart cards that have both A and B. For example, ``trusted input + trusted output trusted input'', because any smart card that has trusted input only can be simulated by a smart card that has both trusted input and trusted output.