Encryption and National Security versus Liberty

In the 1990s, in what might be called the first battle of the Crypto War, the government classified encryption as a munition and restricted its export.  While opposing export in general, the government was licensing the export of implementations that were restricted to a forty bit key.  Of course, 56 bit was then the norm and, at the time, expensive for the NSA to crack.  

IBM had just purchased Lotus Notes and wanted to,export it.  In order to get a license, they negotiated an agreement under which they would encrypt 16 bits of the 56 bit message key under a public key provided by the government and attach it to the message or object.  This would mean that while the work factor anyone else would be 56 bits, for the government it would be only 40 bits.

Viewed today, 40 bit encryption is trivial; twenty years ago it was strong enough that, while the government could read any message that it wanted to, it could not read every message that it wanted to.  Said another way, it would be able to do intelligence, or even investigation, but it still would not be able to engage in mass surveillance.  

Moreover, we believed that the NSA only collected,traffic that crossed our borders, that it could not be used against citizens.  We believed that the government could keep,their private key secure. Of course, post "warrant-less surveillance," the routine breaches of government computers, including those of the NSA,and the exponential growth of computing power over a generation, this all seems very naive.  

However, I like,to think that it illustrates that it is possible to craft solutions that grant authorized access to the government, with a work factor measured in weeks to months per message, file, device or key, while presenting all,others with a cost of attack measured in decades or even centuries.   

It also illustrates the fundamental, application, and implementation-induced limitations of any such scheme, limitations that would have to be compensated for.  No such scheme will be fool-proof, nor need it be.  Like our other institutions and tools, it need only work well enough for each intended application and environment. 

Crypto Wars Redux

This morning, while researching another question, I found the following from Aaron Schumann to alt.security, quoting a post to the Risk Forum from me.  While written a quarter of a century ago, it might have been written this morning.

From: schuman@sgi.com (Aaron Schuman)
Newsgroups: alt.security
Subject: Congress to order crypto trapdoor?
Message-ID: <1991apr11 .231215.19779="" dragon.wpd.sgi.com="">
Date: 11 Apr 91 23:12:15 GMT 

The United States Senate is considering a bill that would require
manufacturers of cryptographic equipment to introduce a trap door,
and to make that trap door accessible to law enforcement officials.
If you feel, as I do, that the risk of abuse far outweighs the
potential benefits, please write to Senators Joseph Biden and Dennis
DeConcini, and to the Senators that represent your state, asking that
they propose a friendly amendment to their bill removing this
requirement.

I don't have exact addresses for Senators Biden and DeConcini, and
I hope someone will post them here, but the Washington DC post office
can deliver letters addressed to
Senator Joseph Biden Senator Dennis DeConcini
United States Senate and United States Senate
Washington, DC 20510 Washington, DC 20510

------------------------------
RISKS-LIST: RISKS-FORUM Digest  Wednesday 10 April 1991  Volume 11 : Issue 43
Date:  Wed, 10 Apr 91 17:23 EDT
From: WHMurray@DOCKMASTER.NCSC.MIL
Subject:  U.S. Senate 266, Section 2201 (cryptographics)
Senate 266 introduced by Mr. Biden (for himself and Mr. DeConcini)
contains the following section:
SEC. 2201. COOPERATION OF TELECOMMUNICATIONS PROVIDERS WITH LAW ENFORCEMENT
It is the sense of Congress that providers of electronic communications
services and manufacturers of electronic communications service equipment shall
ensure that communications systems permit the government to obtain the plain
text contents of voice, data, and other communications when appropriately
authorized by law.
------------------------------
The referenced language requires that manufacturers build trap-doors
into all cryptographic equipment and that providers of confidential
channels reserve to themselves, their agents, and assigns the ability to
read all traffic. 

Are there readers of this list that believe that it is possible for
manufacturers of crypto gear to include such a mechanism and also to reserve
its use to those "appropriately authorized by law" to employ it?
Are there readers of this list who believe that providers of electronic
communications services can reserve to themselves the ability to read all the
traffic and still keep the traffic "confidential" in any meaningful sense?
Is there anybody out there who would buy crypto gear or confidential services
from vendors who were subject to such a law? 

David Kahn asserts that the sovereign always attempts to reserve the use of
cryptography to himself.  Nonetheless, if this language were to be enacted into
law, it would represent a major departure.  An earlier Senate went to great
pains to assure itself that there were no trapdoors in the DES. Mr. Biden and
Mr. DeConcini want to mandate them.  The historical justification of such
reservation has been "national security;" just when that justification begins
to wane, Mr. Biden wants to use "law enforcement."  Both justifications rest
upon appeals to fear. 

In the United States the people, not the Congress, are sovereign; it should not
be illegal for the people to have access to communications that the government
cannot read.  We should be free from unreasonable search and seizure; we should
be free from self-incrimination.  The government already has powerful tools of
investigation at its disposal; it has demonstrated precious little restraint in
their use. 

Any assertion that all use of any such trap-doors would be only
"when appropriately authorized by law" is absurd on its face.  It is not
humanly possible to construct a mechanism that could meet that
requirement;  any such mechanism would be subject to abuse.
I suggest that you begin to stock up on crypto gear while you can still get it.
Watch the progress of this law carefully.  Begin to identify vendors across the
pond. 

William Hugh Murray, Executive Consultant, Information System Security 21
Locust Avenue, Suite 2D, New Canaan, Connecticut 06840       203 966 4769

We fought this battle once and thought that we won the war.