Secure Systems under NZ-COM
                          by Joe Wright
                            13 Jul 88

NZCPR.ZRL  is a version of ZCPR34 with an extended  and  somewhat 
elaborate  security system built in.  It works around the  states 
of DRVEC, MAXDRV, MAXUSR, WHEEL, Z3NDIR and PASSWORD.

A secure system under Z34 will usually have some directory  areas 
'open' to the user and others not.  Try to think of the system as 
a  big  box  of secure directories with a  smaller  box  of  open 
directories inside it.

User #

15
...
 5
 4
___________________
                  |
 3                |
 2                |
 1   The Box      |
 0                |
                  |
Drive     A    B  |  C    D    E    F    ...

By setting MAXDRV to B (2) and MAXUSR to 3 we allow  unrestricted 
access  from  A0  through B3.  Either DIR or  DU  references  are 
permitted within the box.  All others are somehow protected.  The 
DRVEC  word 'protects' any drive with its associated  bit  clear, 
even if it is within the 'box'.  

All directories outside the box are inaccessable unless they have 
a name in the current Z3NDIR.  With the WHEEL off, the user  must 
specify the directory by NAME.  DU reference is not allowed.   If 
the  NAME  has an associated PASSWORD, the user  must  type  this 
correctly as well to gain any access to the directory.

With  the WHEEL on, we are still restricted to those  directories 
with NAMES although DU reference to NAMED directories is  allowed 
and no password checking is required.

You can create a very secure system by reducing the 'box' to  A0:  
The  user  has access to all NAMED directories outside  the  box, 
unless they are passworded and he doesn't know the password.

You  may  give  certain users special access to  other  areas  by 
allowing CD to change the current Z3NDIR.  You can allow 'almost' 
anything  without  giving him the WHEEL (Don't  give  anyone  the 
WHEEL. That belongs to you).

I hope that Jay Sage is able to give a more coherent  explanation 
of  all  this  in the up-coming  ZCPR34  documentation.   In  the 
meantime, simply try it out.