[IP] Master Key Copying Revealed (Matt Blaze of ATT Labs)

Bill Stewart bill.stewart at pobox.com
Tue Jan 28 04:03:19 EST 2003


At 09:12 PM 01/26/2003 -0500, Donald Eastlake 3rd wrote:
>It's just silly to spend, say, $50 more, on a more secure lock unless
>you are really willing, in the forseeable future, to spend hundreds or
>thousands of dollars or even more on other weaknesses to make most of
>them approximately as strong.

Defense in depth is certainly important for physical security,
for serial attacks as well as parallel attacks.
A long long time ago, in a phone company far far away,
about two floors down from where Matt Blaze was working,
I ran the computers and some other operations
for a workroom that did classified government processing.
The higher-security data lived in safes when we weren't actively using it,
as did any classified backup magtapes.  (Computers were still big then,
and the removable disk packs were roughly 14" diameter, 8" high, 250MB.)
The TEMPEST room they lived in didn't have locks on it,
just annoyingly unreliable electrical airlock doors.
It lived inside a room that had several inches of sheetrock and wiremesh walls,
and a door that had two locks - a classified-rated Sergeant & Greenleaf
mechanical combination lock, which we used when the room was unattended,
and an electronic-pushbutton combination lock which was enough when
the room wasn't attended by a guard at the front desk,
plus there were motion-detector alarms set when it wasn't attended.
Army Reg 380-380 didn't require that the room be impregnable to
people with sawzalls and dynamite - just that it be hard to break into,
and extremely hard to break into without leaving an obvious mess,
and a guard schedule appropriate for the level of difficulty breaking in.

>There are also other factors in planning physical security. I've had to
>actually break through a wall because an electronic lock's battery back
>up power died because the transformer for a building was being replaced
>and it had absolutely no power feed for a few days. The repair of such
>wall damage is an expense. Mechanical devices do not have the problem of
>requiring power (PS: Brass is self lubricating).

One of the screws holding the S&G lock to the doorframe came loose
and jammed the lock.  We had to call a locksmith to drill it out,
and it took him about the required two hours to do it.
(If there'd been an emergency, we'd have sawzalled the door.)
The electronic lock jammed a couple of times, and it wasn't hard to
jimmy the door enough with a fireman's prybar to use a screwdriver to
open the latch, but we let the guards know before we started.

The real security problem was when somebody built another secure lab
next door, with what was supposed to be a high-spookiness-quality alarm system;
it took a long time to figure out that most of the false alarms were from
the guards' walkie-talkies causing electrical interference,
and got them instructed not to press talk in that hallway unless
there was something seriously suspicious going on...
and got them instructed to call the other guy, not me, if there was an 
alarm :-)



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