Availability of sense keys

[Landau, Charles]

The general availability of a sense key which can turn a node key into a
read-only node key violates the ability to construct synthetic node keys. A
synthetic node key can be implemented using a red segment key. The effect of
the sense key on a synthetic node will be different from the effect on a
real node. That is why sense keys are closely held. 

> -----Original Message-----
> From:	Jonathan S. Shapiro [SMTP:jsshapiro@earthlink.net]
> Sent:	Friday, April 10, 1998 4:57 PM
> To:	eros-arch@eros.cis.upenn.edu
> Subject:	Re: Re-writing of Process key issue
> 
> The source of the change was independent in the two cases.  One was a
> simple thinko on my part.  The other has a principled basis.
> 
> There is no reason for the discrim key to be closely held.  I was
> simply mistaken on this.
> 
> The operation that is easier in EROS is obtaining a weak, read-only
> node key, which is the equivalent to a sensory key in KeyKOS.
> 
> After some discussion, Norm and I came to the conclusion that
> fabricating a weak, read-only key should be a generally accessable
> operation.  The guiding principle is that the ability to *reduce*
> authority should not be restricted, and turning a segment into a
> "sense" segment is such an operation.
> 
> 
> shap