strong crypto => increase in rubber-hose attacks?

I remember seeing a news report a while back that said the number of violent  
car thefts has increased because more people are using sophisticated car alarms  
and/or car tracking devices.

According to the news report, instead of breaking into cars when the owners  
were away, car thieves would wait until the owner shows up and deactivates the  
car alarm.  The thieves then pounce on the owner, killing or severely injuring  
him/her, and take the car.

Regardless of the actually magnitude of this problem (the media would call  
increase of 1 a major new trend) this did get me to thinking.


Assume you use strong crypto to protect your secrets.

Assume a lot of people start using crypto to protect their secrets.

Assume there are people who want to discover these secrets.


Might we some day see an increase in the number physical attacks as bad guys  
resort to rubber-hose methods to get at the keys that protect the secrets?

Don't get me wrong, I'm still in favor of using strong crypto.  I'm just  
wondering about some of the social implications.


Jim_Miller@suite.com

Jim Miller writes :
> 
> Assume you use strong crypto to protect your secrets.
> 
> Assume a lot of people start using crypto to protect their secrets.
> 
> Assume there are people who want to discover these secrets.
> 
> 
> Might we some day see an increase in the number physical attacks as bad guys  
> resort to rubber-hose methods to get at the keys that protect the secrets?
> 

I think this phenomenon is more or less inevitable, unless serious thought
is given to a way to prevent it. Let's take a simple example and progress
to a more complex scenario:

If I want your money, I could steal your ATM card and try to deduce the PIN
number (tough), or I could wait in the bushes with a .44 until you use the 
ATM and either steal the money you get out (easy) or convince you to tell me
the PIN number (harder, although a .44 is remarkably persuasive). However,
it's easy for you to lock me out of your accounts by changing the PIN number
the next day - to get continued access to your account, I'd have to get the
PIN number and then kill you (begging your pardon, of course). Even if I did
all that, all I'd have is a bank account. Hardly worth it.

If I want your *life* (metaphorically speaking; your network connections, your
digicash, your 'reputation capital', etc.) and all I have to do to get it is
beat your PGP pass phrase out of you and kill you afterwards, you're in much
more danger. I could lie in wait, get your pass phrase, (ahem) remove the 
evidence, and step into your net.shoes the next day.     

Bottom line: As the value protected by our encryption systems increases, we
must devote more effort to the solution of problems like the thug with the .44
(or the jealous co-worker; insert favorite bogey-man here) who wants our 
password. Key revocation certificates are nice, for example, assuming you are
able to issue one - 'dead men revoke no keys,' however. Duress codes seem 
like a better deal; even though the enemy may kill you after you give him 
a code that (seemingly) works, your 'estate' would be protected. What we
*really* need is a hat trick that makes strong-arm tactics useless - 
any ideas? When the tactic of beating a pass phrase out of a citizen becomes
as stupid as killing for a PIN number, we'll know we've succeeded.

<Shudder>
 
Damn! My coffee's gone cold. I'm off to get a refill- talking about killing
people has given me a definite chill. Not my favorite topic.

........................................................................
Philippe D. Nave, Jr.   | The person who does not use message encryption
pdn@dwroll.dw.att.com   | will soon be at the mercy of those who DO...
Denver, Colorado USA    | PGP public key: by arrangement.

It seems like it would be relatively simple to program in a sort of dead-man
switch at the time of creation of the secret key.  As with other double-pass
systems, use of the second phrase works once, but either/both sends a silent
alarm and changes the passphrase to get the secret key.  If you want to get
fancy, you might even program in a script that, on activation of the 2nd
"duress" phrase would run around re-encrypting everything with a second
private key.

As you can imagine, there are increasing levels of personal security you
might employ.  For example, using the duress phrase might be set up to
change the pass-phrase to something *you* don't know but which is known by a
trusted other party (wife, mother, agent/lawyer, etc.).  Knowing this phrase
doesn't help them since that phrase can't access your secret until *after*
you've given the duress phrase and the software has disabled your normal
access phrase.

Depends how paranoid you want to be and how valuable your data is, I
guess...

--Alan Wexelblat, Reality Hacker, Author, and Cyberspace Bard
Media Lab - Advanced Human Interface Group	wex@media.mit.edu
Voice: 617-258-9168, Pager: 617-945-1842	PUBLIC KEY available by request
"To pleasure!" "To passion!" "To paradise!" "To pain!" "Tonight!"

Philippe Nave:
> As the value protected by our encryption systems increases, we
> must devote more effort to the solution of problems like the thug...

Distributed pass phrases have been mentioned, as have distress codes 
and dead-man switches.  Along with distributed pass phrases I'd add
distributed keys with M-out-of-N voting, for valuable shared data
(eg corporate data, family bank account).  Other options include:

	* steganography and foiling traffic analysis: don't let the
	thugs know you have valuable encrypted data in the first
	place.
	* multiple keys with multiple (easy to remember!) pass
	phrases. We use different keys for our house, car, safes, etc.
	as well as different passwords for different accounts,
	and this will likely be also true for our encryption
	strategies.  For example, it's a good idea to encrypt
	files on one's disk with a different key than one
	uses to receive e-mail.

The ability to choose high-entropy but easy to rememember pass
phrases is an interesting art.  One strategy  is to pick
short pass phrases with high entropy (eg by requiring mixed cases, 
letters+numbers, etc.)  PGP allows one to pick a long phrase, 
easier to remember, with less entropy per character but more total entropy.
I despise the current situation where I have to choose a bunch of
difficult to remember alphanumeric codes for different kinds of
accounts, ATM access, etc.

Nick Szabo					szabo@netcom.com