Description

A sensory key is similar to (in some cases identical with) a read-only key, with the additional property that all keys obtained through it will be weakened to sensory authority. This provides a way to hand a client a key to an object and ensure that all of the objects that are transitively reachable through the initial key will be immutable to the client. A sensory key conveys no authority to modify the designated object.

The sensory version of a key is defined as follows:

• The sensory version of a node key is a node key to the same node with the same key info field, except that the no-call, read-only, and weak attributes are guaranteed to be set.

• The sensory version of an address space key is a read-only, no-call, weak version of the address space key.

• The sensory version of a number key is the same key.

• The sensory version of a page key is a read-only page key to the same page.

• The sensory version of the discrim key is the same key.

• The sensory version of all other keys is the void key.

A significant difference between EROS and previous systems implementing this facility is that sensory keys are easily obtained.