From: Fred Cisin <>
Date: Mon Sep 27 15:51:59 1999

On Mon, 27 Sep 1999, Tony Duell wrote:
> > If you don't eliminate non-authorized access to the hardware, then how
> > could you eliminate non-operator use of the control panel? A
> > non-operator could merely bypass the lock, or replace it with their own.
> > Or is it merely intended to be a polite request and reminder?
> Basically, the latter. Suppose you have a PDP11 in a public-access
> terminal room in a school or university. Students might be able to frob a
> few switches without getting caught, but they sure aren't going to be
> able to pull units out of racks, dismantle frontpanels and connect wires
> to the back of the keyswitch without people noticing :-)
> Locking the panel prevents people crashing the machine (or worse) from the
> panel. If you've got physical access to the machine and wouldn't be
> stopped from dismantling it, then I can assure you that having the panel
> locked is not going to hinder you much. Mind you, if you've got that sort
> of access, you could remove disk packs (or tapes) and read them on your
> own machine.

Prevention of casual or even accidental tampering is a reasonable goal.
Not sure why that would require an ACE or Medeco "difficult-to-pick" lock.

> > ANY properly designed and installed lock must be unlocked before it can be
> > removed.
> Hmmm... I can think of plenty of locks, including most (house) door locks
> where, although the door (or whatever) has to be open to dismantle the
> lock, you don't have to have the key, or have the lock in the unlocked
> position to do so. Try locking one of your locks with the door open, and
> see if you can take it apart without unlocking it.

Well, I could fall back on my phrase "properly designed" :-) But what I
meant included locks that HAD BEEN unlocked, bypassed, or compromised in
order to open the door or access the "secure" side, even if now relocked.
A properly installed house lock can not be removed from the outside until
it has been opened or accessed from the "secure" side. Many low security
house locks, such as most Schlage, should be unlocked for disassembly,
therefore making it harder to rekey them unless you have the key or pick

Some automotive steering-wheel/ignition locks have to be in the unlocked
position for removal. Most of the old NON-steering-wheel type of ignition
locks (except certain Saabs which lock shift linkage) provide nothing more
than a reminder.
Received on Mon Sep 27 1999 - 15:51:59 BST

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