[117104] in Cypherpunks
RE: Project: Hardening Crypto Against Big Brother's "BlackBag" Intrusions
daemon@ATHENA.MIT.EDU (Kurt Buff)
Thu Aug 26 14:18:25 1999
From: "Kurt Buff" <kurtbuff@lightmail.com>
To: "'Sunder'" <sunder@brainlink.com>
Cc: <cypherpunks@cyberpass.net>
Date: Thu, 26 Aug 1999 10:44:37 -0700
Message-ID: <001701beefea$aadeb3a0$1a01010a@pigfarm.org>
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Reply-To: "Kurt Buff" <kurtbuff@lightmail.com>
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Sounds like this came out of a beer fest...
All I really want the thing for is as a decoder/authentication key
for a program that is used as a boot loader for an OS, without which
the machine is useless, because the boot loader decrypts the HD.
The boot loader should have enough smarts to respond to an
authentication procedure, and pass cryptographic tests such that the
USB key can be assured that the program hasn't been tampered with.
Granted, this is no small task, but it should be doable by someone
with more technical knowledge than I have, which is woefully limited.
It may require a different approach, such as a palm-sized device for
more computing power, but still...
| -----Original Message-----
| From: Sunder [mailto:sunder@brainlink.com]
| Sent: Thursday, August 26, 1999 09:36
| To: kurtbuff@lightmail.com
| Cc: cypherpunks@cyberpass.net
| Subject: Re: Project: Hardening Crypto Against Big Brother's
| "BlackBag"
| Intrusions
|
|
| I've spent a few hours shooting the shit with an old
| pro-crypto friend, and
| bouncing ideas off (and drinking.) :)
|
| It's losing proposition IMHO as far as I can figure (unless
| someone can figure
| out some other thing.)
|
| So far the system seems to be a big box with encrypted disks
| that uses a small
| box with enough CPU to decrypt the disks and let you access
| it. Small box can
| be a PDA or a PC Card... You play good guy, I play bad guy:
|
| Here are the flaws/fixes:
|
| If I backdoor the big box, you login with your little box and
| start doing
| work. I can now cache the plaintext somewhere where I can get to
| it.
|
| If you use the big box for disk access only (say as a file
| server) and use the
| small box to do work, (the protocol doesn't allow any
| programs to run on your
| small box from the big box) then you must keep it with you at
| all times to
| prevent it from being backdoored.
|
| So now I'd have to somehow get my hands on your small box to bug
| it.
|
| There are several ways to do this.
|
| Most importantly at some point you will sleep. When you do
| (and your sleep
| may be chemically enhanced) I could get to your small box and
| add the back
| doors. So you'd have to add some C4 to the small box to blow
| my fingers off
| if I touch it. Barring sleep, you could be mugged, pick
| pocketed, etc...
|
| If I have tempest equipment I could get at your display and
| even figure out
| what your small box's CPU is doing. So you'll also have to
| tempest proof your
| machine somehow. It's no longer such a small box. :)
|
| If you do have some sort of trap that will blow my fingers
| off, then I could
| attempt several things: freeze it to near zero to disarm the
| trap, wait until
| the batteries run out, X-Ray it to find out where the trap
| is, etc. You'll
| have to put sensors in to watch for temperature extremes,
| XRays and blow the
| C4 before the circuits that do that die, etc... if the
| battery gets too low,
| fry all data on it, etc...
|
| This is the type of equipment you will need. The small box
| is looking more
| and more like a low end portable computer. I'd say Palm, but
| their CPUs
| aren't going to have enough horse power to do real time disk
| decryption. I'm
| not quite pushing a mickeysoft product so don't get your
| panties in a bunch,
| but wince boxes are based on RISC cpu's, and may have
| flashable ROM's... If
| they do, you flash'em with your own OS, etc... Better yet
| one of the Libretto
| or small mini Sony Vaio's...
|
| You'll also have to keep this box off the net incase I do
| manage to install
| back doors.
|
|
| Keep the keys on a PC card encrypted with a passphrase, but
| typing it in
| shouldn't be the only thing. Do all your work from this
| small machine. (Of
| course CPU power will limit you a lot.)
|
| You'll also need some sort of dead man's switch that's easily
| accessible. A
| few mercury switches well positioned could arm it, and if you
| don't type in
| the right passphrase in the right amount of time, it wipes
| the card, maybe
| beeps at you in a pattern (or better yet plays Yankee Doodle
| Dandy :^), to let
| you know it's too late, and then blows itself to bits.
|
| When you do use your key, it should wipe the card incase you
| don't get a
| chance to do so, or they manage to eject it. When you tell
| it to shut down,
| it should write the key back, but with a new random salt.
|
|
| (There are also issues of key recovery if the hardware does
| go bad, or if your
| pet cat/dog/lizard/ferret/rodent lands on it and sets off the
| deadman switch,
| but presumably, you wouldn't leave the machine lying around
| at all. If you do
| you open yourself up for a hardware bug being planted. If
| you do put an XRay
| detector in it, be sure to disable it when you go through
| airports incase they
| don't do hand inspections - but then C4 becomes an issue, etc...)
|
| It's not perfect, it's not easy, but it's a thought... Any more?
|
|
| Kurt Buff wrote:
| >
| > -----BEGIN PGP SIGNED MESSAGE-----
| >
| > Agree with your comments, but the site does mention a 12MHz
| processor
| > and 128bytes(?!) of RAM, and a physical fuse to prevent
| file readout.
| > All sounds like a good start, but needs good verification
| to be sure.
|
| --
| ---------------------------- Kaos Keraunos Kybernetos
| --------------------
| + ^ + Sunder "The real aim of current policy
| is to /|\
| \|/ sunder@brainlink.com ensure the continued
| effectiveness of /\|/\
| <--*--> -------------------- OF US information warfare assets
| against\/|\/
| /|\ You're on the air. individuals,businesses and
| governments \|/
| + v + Say 'Hi' to Echelon in Europe and elsewhere" -- Ross
| Anderson
| ---------------------------- http://www.sunder.net
| -----------------------
| "The day that Microsoft makes a product that doesn't suck is
| the same day
| they start making vacuum cleaners."
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