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Interesting narrative on transient electromagnetic pulse emanation standard. The text is somewhat disarrayed.
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Interesting narrative on transient electromagnetic pulse emanation standard. The text is somewhat disarrayed.
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Eavesdropping On the Electromagnetic Emanations of
Digital Equipment: The Laws of Canada, England and
the United States

Copyright (C) 1989 By Christopher Seline

This document is a rough draft. The Legal Sections
are overviews. They will be significantly
expanded in the next version.

We in this country, in this generation, are -- by
destiny rather than choice -- the watchmen on the
walls of world freedom.1
-President John F. Kennedy

In the novel 1984, George Orwell foretold a future where
individuals had no expectation of privacy because the state
monopolized the technology of spying. The government
watched the actions of its subjects from birth to death. No
one could protect himself because surveillance and counter-
surveillance technology was controlled by the government.

This note explores the legal status of a surveillance
technology ruefully known as TEMPEST2. Using TEMPEST
technology the information in any digital device may be
intercepted and reconstructed into useful intelligence
without the operative ever having to come near his target.
The technology is especially useful in the interception of
information stored in digital computers or displayed on
computer terminals.

1. Undelivered speech of President John F. Ken-
nedy, Dallas Citizens Council (Nov. 22, 1963) 35-36.
2. TEMPEST is an acronym for Transient Electromag-
netic Pulse Emanation Standard. This standard sets
forth the official views of the United States on the
amount of electromagnetic radiation that a device may
emit without compromising the information it is pro-

June 7, 1990

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The use of TEMPEST is not illegal under the laws of the
United States3, or England. Canada has specific laws
criminalizing TEMPEST eavesdropping but the laws do more to
hinder surveillance countermeasures than to prevent TEMPEST
surveillance. In the United States it is illegal for an
individual to take effective counter-measures against
TEMPEST surveillance. This leads to the conundrum that it
is legal for individuals and the government to invade the
privacy of others but illegal for individuals to take steps
to protect their privacy.

The author would like to suggest that the solution to this
conundrum is straightforward. Information on pro-
tecting privacy under TEMPEST should be made freely
available; TEMPEST Certified equipment should be legally
available; and organizations possessing private information
should be required by law to protect that information
through good computer security practices and the use of
TEMPEST Certified equipment.

Spying is divided by professionals into two main types:
human intelligence gathering (HUMINT) and electronic
intelligence gathering (ELINT). As the names imply, HUMINT
relies on human operatives, and ELINT relies on
technological operatives. In the past HUMINT was the sole
method for collecting intelligence.4 The HUMINT operative
would steal important papers, observe troop and weapon
movements5, lure people into his confidences to extract
secrets, and stand under the eavesdrip6 of houses,
eavesdropping on the occupants.

cessing. TEMPEST is a defensive standard; a device
which conforms to this standard is referred to as TEM-
PEST Certified.
The United States government has refused to declassi-
fy the acronym for devices used to intercept the
electromagnetic information of non-TEMPEST Certified
devices. For this note, these devices and the
technology behind them will also be referred to
as TEMPEST; in which case, TEMPEST stands for
Transient Electromagnetic Pulse Surveillance Technolo-
The United States government refuses to release
details regarding TEMPEST and continues an organized
effort to censor the dissemination of information
about it. For example the NSA succeeded in shut-
ting down a Wang Laboratories presentation on TEM-
PEST Certified equipment by classifying the contents
of the speech and threatening to prosecute the
speaker with revealing classified information. [cite
3. This Note will not discuses how TEMPEST re-

June 7, 1990

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As technology has progressed, tasks that once could only
be performed by humans have been taken over by
machines. So it has been with spying. Modern satellite
technology allows troop and weapons movements to be observed
with greater precision and from greater distances than a
human spy could ever hope to accomplish. The theft of
documents and eavesdropping on conversations may now be
performed electronically. This means greater safety for the
human operative, whose only involvement may be the placing
of the initial ELINT devices. This has led to the
ascendancy of ELINT over HUMINT because the placement and
monitoring of ELINT devices may be performed by a technician
who has no training in the art of spying. The gathered
intelligence may be processed by an intelligence expert,
perhaps thousands of miles away, with no need of field

ELINT has a number of other advantages over HUMINT. If a
spy is caught his existence could embarrass his employing
state and he could be forced into giving up the identities
of his compatriots or other important information. By its
very nature, a discovered ELINT device (bug) cannot give up
any information; and the ubiquitous nature of bugs provides
the principle state with the ability to plausibly deny
ownership or involvement.
lates to the Warrant Requirement under the United
States Constitution. Nor will it discuss the Consti-
tutional exclusion of foreign nationals from the War-
rant Requirement.
4. HUMINT has been used by the United States
since the Revolution. "The necessity of procuring
good intelligence is apparent & need not be further
urged -- All that remains for me to add is, that you
keep the whole matter as secret as possible. For
upon Secrecy, Success depends in Most Enterprises of
the kind, and for want of it, they are generally de-
feated, however well planned & promising a favorable
issue." Letter of George Washington (Jul. 26, 1777).
5. "... I wish you to take every possible pains in
your powers, by sending trusty persons to Staten
Island in whom you can confide, to obtain Intelli-
gence of the Enemy's situation & numbers -- what
kind of Troops they are, and what Guards they have
-- their strength & where posted." Id.
6. Eavesdrip is an Anglo-Saxon word, and refers to
the wide overhanging eaves used to prevent rain from
falling close to a house's foundation. The eavesdrip
provided "a sheltered place where one could hide to
listen clandestinely to conversation within the

June 7, 1990

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ELINT devices fall into two broad categories:
trespassatory and non-trespassatory. Trespassatory bugs
require some type of trespass in order for them to function.
A transmitter might require the physical invasion of the
target premises for placement, or a microphone might be
surreptitiously attached to the outside of a window. A
telephone transmitter can be placed anywhere on the phone
line, including at the central switch. The trespass comes
either when it is physically attached to the phone line, or
if it is inductive, when placed in close proximity to the
phone line. Even microwave bugs require the placement of
the resonator cone within the target premises.7

Non-trespassatory ELINT devices work by receiving
electromagnetic radiation (EMR) as it radiates through the
aether, and do not require the placement of bugs. Methods
include intercepting8 information transmitted by satellite,
microwave, and radio, including mobile and cellular phone
transmissions. This information was purposely transmitted
with the intent that some intended person or persons would
receive it.

Non-trespassatory ELINT also includes the interception of
information that was never intended to be transmitted.
All electronic devices emit electromagnetic radiation. Some
of the radiation, as with radio waves, is intended to
transmit information. Much of this radiation is not
intended to transmit information and is merely incidental to
whatever work the target device is performing.9 This
information can be intercepted and reconstructed into a
coherent form. With current TEMPEST technology it is
possible to reconstruct the contents of computer video
display terminal (VDU) screens from up to a kilometer
distant10; reconstructing the contents of a computer's
memory or the contents of its mass storage devices is more
complicated and must be performed from a closer distance.11
The reconstruction of information via EMR, a process for
which the United States government refuses to declassify
either the exact technique or even its name12, is not
limited to computers and digital devices but is applicable
to all devices that generate electromagnetic radiation.13
TEMPEST is especially effective against VDUs because they
produce a very high level of EMR.14
7. Pursglove, How Russian Spy Radios Work, RADIO
ELECTRONICS, 89-91 (Jan 1962).
8. Interception is an espionage term of art and
should be differentiated from its more common usage.
When information is intercepted, the interceptor as
well as the intended recipient receive the informa-
tion. Interception when not used as a term of art
refers to one person receiving something intended for
someone else; the intended recipient never receives
what he was intended to receive.

June 7, 1990

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"[C]ables may act as an antenna to transmit
the signals directly or even both receive the
signals and re-emit them further away from the
source equipment. It is possible that cables
acting as an antenna in such a manner could
transmit the signals much more efficiently
than the equipment itself...A similar effect
may occur with metal pipes such as those for
domestic water supplies. ... If an earthing
[(grounding)] system is not installed correctly
such that there is a path in the circuit with
a very high resistance (for example where paint
prevents conduction and is acting as an insu-
lator), then the whole earthing system could
well act in a similar fashion to an antenna. ...
[For a VDU] the strongest signals, or harmonics
thereof, are usually between 60-250 MHz approx-
imately. There have however been noticeable
exception of extremely strong emissions in
the television bands and at higher frequencies
between 450-800 MHz. Potts, Emission Security,

9. There are two types of emissions, conducted and
radiated. Radiated emissions are formed when com-
ponents or cables act as antennas for transmit the
EMR; when radiation is conducted along cables or other
connections but not radiated it is referred to as "con-
ducted". Sources include cables, the ground loop,
printed circuit boards, internal wires, the power
supply to power line
10. The TEMPEST ELINT operator can distinguish between
different VDUs in the same room because of
the different EMR characteristics of both homo and
heterogeneous units. "[T]here is little comparison
between EMR characteristics from otherwise comparable
equipment. Only if the [VDU] was made with exactly
the same components is there any similarity. If
some of the components have come from a different
batch, have been updated in some way, and especial-
ly if they are from a different manufacturer,
then completely different results are obtained. In
this way a different mark or version of the same [VDU]
will emit different signals. Additionally because
of the variation of manufacturing standards between
counties, two [VDUs] made by the same company but
sourced from different counties will have entirely
different EMR signal characteristics...From this it way
be thought that there is such a jumble of emissions
around, that it would not be possible to isolate those
from any one particular source. Again, this is not the
case. Most received signals have a different line

June 7, 1990

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ELINT is not limited to governments. It is routinely used
by individuals for their own purposes. Almost all
forms of ELINT are available to the individual with either
the technological expertise or the money to hire someone
synchronization, due to design, reflection, in-
terference or variation of component tolerances. So
that if for instance there are three different
signals on the same frequency ... by fine tuning
of the RF receiver, antenna manipulation and
modification of line synchronization, it is possi-
ble to lock onto each of the three signals separately
and so read the screen information. By similar
techniques, it is entirely possible to discriminate
between individual items of equipment in the same
room." Potts, supra note 9. For a discussion of
the TEMPEST ELINT threat See e.g., Memory Bank,
AMERICAN BANKER 20 (Apr 1 1985); Emissions from Bank
Computer Systems Make Eavesdropping Easy, Expert
Says, AMERICAN BANKER 1 (Mar 26 1985); CRT spying:
a threat to corporate security, PC WEEK (Mar 10
11. TEMPEST is concerned with the transient elec-
tromagnetic pulses formed by digital equipment. All
electronic equipment radiates EMR which may be
reconstructed. Digital equipment processes informa-
tion as 1's and 0's--on's or off's. Because of this,
digital equipment gives off pulses of EMR. These
pulses are easier to reconstruct at a distance than
the non-pulse EMR given off by analog equipment.
For a thorough discussion the radiation problems of
broadband digital information see e.g. military
standard MIL-STD-461 REO2; White supra note 9,
12. See supra note 2.
13. Of special interest to ELINT collectors are
EMR from computers, communications centers and
avionics. Schultz, Defeating Ivan with TEMPEST, DE-
14. The picture on a CRT screen is built up
of picture elements (pixels) organized in lines
across the screen. The pixels are made of materi-
al that fluoresces when struck with energy. The en-
ergy is produced by a beam of electrons fired from an
electron gun in the back of the picture tube. The
electron beam scans the screen of the CRT in a regular
repetitive manner. When the voltage of the beam is
high then the pixel it is focused upon emits photons
and appears as a dot on the screen. By selective-
ly firing the gun as it scans across the face of
the CRT, the pixels form characters on the CRT screen.
The pixels glow for only a very short time
and must be routinely struck by the electron beam to
stay lit. To maintain the light output of all the

June 7, 1990

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with the expertise. Governments have attempted to
criminalize all use of ELINT by their subjects--to protect
the privacy of both the government and the population.

In the United States, Title III of the Omnibus Streets and
Crimes Act of 196815 criminalizes trespassatory ELINT as the
intentional interception of wire communications.16 As ori-
ginally passed, Title III did not prohibit non-
trespassatory ELINT,17 because courts found that non-wire
communication lacked any expectation of p2IIIrivacy.18 The
Electronic Communications Privacy Act of 198619 amended
Title III to include non-wire communication. ECPA was
specifically designed to include electronic mail, inter-
computer communications, and cellular telephones. To
accomplish this, the expectation of privacy test was
pixels that are supposed to be lit, the electron beam
traverses the entire CRT screen sixty times a second.
Every time the beam fires it causes a high voltage
EMR emission. This EMR can be used to reconstruct
the contents of the target CRT screen. TEMPEST
ELINT equipment designed to reconstruct the informa-
tion synchronizes its CRT with the target CRT. First,
it uses the EMR to synchronize its electron gun with
the electron gun in the target CRT. Then, when the
TEMPEST ELINT unit detects EMR indicating that the tar-
get CRT fired on a pixel, the TEMPEST ELINT unit fires
the electron gun of its CRT. The ELINT CRT is in
perfect synchronism with the target CRT; when the tar-
get lights a pixel, a corresponding pixel on the TEM-
PEST ELINT CRT is lit. The exact picture on the tar-
get CRT will appear on the TEMPEST ELINT CRT. Any
changes on the target screen will be instantly re-
flected in the TEMPEST ELINT screen.
TEMPEST Certified equipment gives off emissions
levels that are too faint to be readily detected.
Certification levels are set out in National
Communications Security Information Memorandum
5100A (NACSIM 5100A). "[E]mission levels are
expressed in the time and frequency domain, broadband
or narrow band in terms of the frequency domain, and
in terms of conducted or radiated emissions." White,
supra, note 9, 10.1.
For a thorough though purposely misleading dis-
cussion of TEMPEST ELINT see Van Eck, Electromagnetic
Radiation from Video Display units: An Eavesdropping
Risk?, 4 Computers & Security 269 (1985).
15. Pub. L. No. 90-351, 82 Stat. 197. The Act
criminalizes trespassatory ELINT by individuals as
well as governmental agents. cf. Katz v. United
States, 389 U.S. 347 (1967) (Fourth Amendment prohibits
surveillance by government not individuals.)

June 7, 1990

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As amended, Title III still outlaws the electronic
interception of communications. The word "communications"
indicates that someone is attempting to communicate
something to someone; it does not refer to the inadvertent
transmission of information. The reception and
reconstruction of emanated transient electromagnetic pulses
(ETEP), however, is based on obtaining information that the
target does not mean to transmit. If the ETEP is not
intended as communication, and is therefore not transmitted
in a form approaching current communications protocols, then
it can not be considered communications as contemplated by
Congress when it amended Title III. Reception, or
interception, of emanated transient electromagnetic pulses
is not criminalized by Title III as amended.

In England the Interception of Communications Act
198521 criminalizes the tapping of communications sent over
public telecommunications lines.22 The interception of
communications on a telecommunication line can take place
with a physical tap on the line, or the passive interception
of microwave or satellite links.23 These forms of passive
interception differ from TEMPEST ELINT because they are
intercepting intended communication; TEMPEST ELINT
intercepts unintended communication. Eavesdropping on the
emanations of computers does not in any way comport to
tapping a telecommunication line and therefore falls outside
the scope of the statute.24
16. 18 U.S.C. 2511(1)(a).
17. United States v. Hall, 488 F.2d 193 (9th Cir.
1973) (found no legislative history indicating
Congress intended the act to include radio-telephone
conversations). Further, Title III only criminalized
the interception of "aural" communications which ex-
cluded all forms of computer communications.
18. Willamette Subscription Television v. Cawood,
580 F.Supp 1164 (D. Or. 1984) (non-wire communications
lacks any expectation of privacy).
19. Pub. L. No. 99-508, 100 Stat. 1848 (codified at 18
U.S.C. 2510-710) [hereinafter ECPA].
9 20. 18 U.S.C. 2511(1)(a) criminalizes the
interception of "any wire, oral or electronic com-
munication" without regard to an expectation of
21. Interception of Communications Act 1985, Long Ti-
tle, An Act to make new provision for and in connection
with the interception of communications sent by
post or by means of public telecommunications
systems and to amend section 45 of the Telecom-
munications Act 1984.
22. Interception of Communications Act 1985 1,
Prohibition on Interception:
(1) Subject to the following provisions of this sec-
tion, a person who intentionally intercepts a com-

9 June 7, 1990

- 9 -

Canada has taken direct steps to limit eavesdropping on com-
puters. The Canadian Criminal Amendment Act of 1985
criminalized indirect access to a computer service.25 The
specific reference to an "electromagnetic device" clearly
shows the intent of the legislature to include the use of
TEMPEST ELINT equipment within the ambit of the legislation.

The limitation of obtaining "any computer service" does lead
to some confusion. The Canadian legislature has not made
it clear whether "computer service" refers to a com-
puter service bureau or merely the services of a
computer. If the Canadians had meant access to any
computer, why did they refer to any "computer service".
This is especially confusing considering the al-
encompassing language of (b) 'any function of a computer

Even if the Canadian legislation criminalizes
eavesdropping on all computers, it does not solve the
problem of protecting the privacy of information. The
purpose of criminal law is to control crime.26 Merely
munication in the course of its transmission by post
or by means of a public telecommunications system
shall be guilty of an offence and liable--
(a) on summary conviction,to a fine not exceeding the
statutory maximum;
(b) on conviction on indictment, to imprisonment for a
term not exceeding two years or to a fine or to both.
23. Tapping (aka trespassatory eavesdropping) is
patently in violation of the statute. "The offense
created by section 1 of the Interception of Communica-
tions Act 1985 covers those forms of eavesdropping on
computer communications which involve "tapping" the
wires along which messages are being passed. One
problem which may arise, however, is the question
of whether the communication in question was inter-
cepted in the course of its transmission by means of
a public telecommunications system. It is technically
possible to intercept a communication at several
stages in its transmission, and it may be a question
of fact to decide the stage at which it enters the
110: COMPUTER MISUSE, 3.30 (1988).
24. "There are also forms of eavesdropping which the
Act does not cover. For example. eavesdropping on a
V.D.U. [referred to in this text as a CRT] screen by
monitoring the radiation field which surrounds it in
order to display whatever appears on the legitimate
user's screen on the eavesdropper's screen. This
activity would not seem to constitute any criminal
COMPUTER MISUSE, 3.31 (1988).

June 7, 1990

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making TEMPEST ELINT illegal will not control its use.
First, because it is an inherently passive crime it is
impossible to detect and hence punish. Second, making this
form of eavesdropping illegal without taking a proactive
stance in controlling compromising emanations gives the
public a false sense of security. Third, criminalizing the
possession of a TEMPEST ELINT device prevents public sector
research into countermeasures. Finally, the law will not
prevent eavesdropping on private information held in company
computers unless disincentives are given for companies that
do not take sufficient precautions against eavesdropping and
simple, more common, information crimes.27

TEMPEST ELINT is passive. The computer or terminal
emanates compromising radiation which is intercepted by the
TEMPEST device and reconstructed into useful information.
Unlike conventional ELINT there is no need to physically
25. 301.2(1) of the Canadian criminal code states
that anyone who without color of right,
(a) obtains, directly or indirectly, any computer ser-
(b) by means of an electromagnetic ... or oth-
er device, intercepts or causes to be intercept-
ed, either directly or indirectly, any function of a
computer system ... [is guilty of an indictable of-
ing the Redrafting of the Preliminary Guidelines "g."
(at an unknown page))
27. There has been great debate over what exactly is
a computer crime. There are several schools of
thought. The more articulate school, and the one to
which the author adheres holds that the category com-
puter crime should be limited to crimes directed
against computers; for example, a terrorist destroying
a computer with explosives would fall into this
category. Crimes such as putting ghost employees
on a payroll computer and collecting their pay are
merely age-old accounting frauds; today the fraud in-
volves a computer because the records are kept on a
computer. The computer is merely ancillary to the
crime. This has been mislabeled computer crime and
should merely be referred to as a fraud perpetrated
with the aid of a computer. Finally, there are infor-
mation crimes. These are crimes related to the pur-
loining or alteration of information. These crimes
are more common and more profitable due to the
computer's ability to hold and access great amounts of
information. TEMPEST ELINT can best be categorized as
a information crime.

June 7, 1990

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trespass or even come near the target. Eavesdropping can be
performed from a nearby office or even a van parked within a
reasonable distance. This means that there is no classic
scene of the crime; and little or no chance of the criminal
being discovered in the act.28

If the crime is discovered it will be ancillary to some
other investigation. For example, if an individual is
investigated for insider trading a search of his residence
may yield a TEMPEST ELINT device. The device would explain
how the defendant was obtaining insider information; but it
was the insider trading, not the device, that gave away the

This is especially true for illegal TEMPEST ELINT per-
formed by the state. Unless the perpetrators are caught in
the act there is little evidence of their spying. A
trespatory bug can be detected and located; further, once
found it provides tangible evidence that a crime took place.

A TEMPEST ELINT device by its inherent passive nature leaves
nothing to detect. Since the government is less likely to
commit an ancillary crime which might be detected there is a
very small chance that the spying will ever be discovered.
The only way to prevent eavesdropping is to encourage the
use of countermeasures: TEMPEST Certified29 computers and

In merely making TEMPEST ELINT illegal the public is
given the false impression of security; they lulled into
believing the problem has been solved. Making certain
actions illegal does not prevent them from occurring. This
is especially true for a TEMPEST ELINT because it is
undetectable. Punishment is an empty threat if there is no
chance of being detected; without detection there can be no
apprehension and conviction. The only way to prevent some
entity from eavesdropping on one's computer or computer
terminal is for the equipment not to give off compromising
emanation; it must be TEMPEST Certified.
28. Compare, for example, the Watergate breakin in
which the burglars were discovered when they re-
turned to move a poorly placed spread spectrum bug.
29. TEMPEST Certified refers to the equipment having
passed a testing and emanations regime specified in
NACSIM 5100A. This classified document sets forth the
emanations levels that the NSA believes digital equip-
ment can give off without compromising the information
it is processing. TEMPEST Certified equipment is
theoretically secure against TEMPEST eavesdropping.
NACSIM 5100A is classified, as are all details
of TEMPEST. To obtain access to it, contractor
must prove that there is demand within the govern-
ment for the specific type of equipment that intend to

June 7, 1990

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The United States can solve this problem by taking a
proactive stance on compromising emanations. The National
Institute of Standards and Technology (NIST30) is in charge
of setting forth standards of computer security for the
private sector. NIST is also charged with doing basic
research to advance the art of computer security. Currently
NIST does not discuss TEMPEST with the private sector. For
privacy's sake, this policy must be changed to a proactive
one. The NIST should publicize the TEMPEST ELINT threat to
computer security and should set up a rating system for
level of emanations produced by computer equipment.31

Further, legislation should be enacted to require the
labeling of all computer equipment with its level of
emanations and whether it is TEMPEST Certified. Only if the
public knows of the problem can it begin to take steps to
solve it.

Title III makes possession of a surveillance device a
crime, unless it is produced under contract to the
government. This means that research into surveillance and
counter-surveillance equipment is monopolized by the
government and a few companies working under contract with
the government. If TEMPEST eavesdropping is criminalized,
then possession of TEMPEST ELINT equipment will be criminal.
Unfortunately,this does not solve the problem. Simple
TEMPEST ELINT equipment is easy to make. For just a few
dollars many older television sets can be modified to
receive and reconstruct EMR. For less than a hundred
dollars a more sophisticated TEMPEST ELINT receiver can be

The problem with criminalizing the possession of TEM-
PEST ELINT equipment is not just that the law will have
little effect on the use of such equipment, but that it will
have a negative effect on counter-measures research. To
successfully design counter-measures to a particular
surveillance technique it is vital to have a complete
empirical understanding of how that technique works.
Without the right to legally manufacture a surveillance
device there is no possible way for a researcher to have the
knowledge to produce an effective counter-measures device.
It is axiomatic: without a surveillance device, it is
certify. Since the standard is classified, the con-
tractors can not sell the equipment to non-secure
governmental agencies or the public. This prevents re-
verse engineering of the standard for its physical
embodiment, the Certified equipment. By preventing
the private sector from owning this anti-
eavesdropping equipment, the NSA has effectively
prevented the them from protecting the information in
their computers.

June 7, 1990

- 13 -

impossible to test a counter-measures device.

A number of companies produce devices to measure the ema-
nations from electrical equipment. Some of these devices
are specifically designed for bench marking TEMPEST
Certified equipment. This does not solve the problem. The
question arises: how much radiation at a particular
frequency is compromising? The current answer is to refer
to NACSIM 5100A. This document specifies the emanations
levels suitable for Certification. The document is only
available to United States contractors having sufficient
security clearance and an ongoing contract to produce
TEMPEST Certified computers for the government. Further,
the correct levels are specified by the NSA and there is no
assurance that, while these levels are sufficient to prevent
eavesdropping by unfriendly operatives, equipment certified
under NACSIM 5100A will have levels low enough to prevent
eavesdropping by the NSA itself.

The accessibility of supposedly correct emanations lev-
els does not solve the problem of preventing TEMPEST
eavesdropping. Access to NACSIM 5100A limits the
manufacturer to selling the equipment only to United States
governmental agencies with the need to process secret
information.33 Without the right to possess TEMPEST ELINT
equipment manufacturers who wish to sell to the public
sector cannot determine what a safe level of emanations is.

30. Previously the Bureau of Standards. The NIST is
a division of the Commerce Department.
31. In this case computer equipment would include all
peripheral computer equipment. There is no use is us-
ing a TEMPEST Certified computer if the printer or the
modem are not Certified.
32. The NSA has tried to limit the availability
of TEMPEST information to prevent the spread of the
For a discussion of the First Amendment and prior
restraint See, e.g. The United States of America v.
Progressive, Inc. 467 F.Supp 990 (1979, WD
Wis.)(magazine intended to publish plans for nuclear
weapon; prior restraint injunction issued), reh.
den. United States v. Progressive Inc. 486 F.Supp 5
(1979, WD Wis.), motion den Morland v. Sprecher
443 US 709 (1979)(mandamus), motion denied United
States v. Progressive, Inc. 5 Media L R (1979, 7th
Cir.), dismd. without op. U.S. v. Progressive, Inc 610
F.2d 819 (1979, 7th Cir.); New York Times, Co. v. Un-
ited States, 403 U.S. 713 (1971)(per
curium)(Pentagon Papers case: setting forth prior
restraint standard which government was unable to

June 7, 1990

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Further those manufacturers with access to NACSIM 5100A
should want to verify that the levels set out in the
document are, in fact, low enough to prevent interception.
Without an actual eavesdropping device with which to test,
no manufacturer will be able to produce genuinely
uncompromising equipment.

Even if the laws allow ownership of TEMPEST Certified
equipment by the public, and even if the public is informed
of TEMPEST's threat to privacy, individuals' private
information will not necessarily by protected. Individuals
may choose to protect their own information on their own
computers. Companies may choose whether to protect their
own private information. But companies that hold the
private information of individuals must be forced to take
steps to protect that information.

In England the Data Protection Act 198434 imposes
sanctions against anyone who stores the personal
information35 on a computer and fails to take reasonable
measures to prevent disclosure of that information. The act
mandates that personal data may not be stored in any
computer unless the computer bureau or data user36 has
registered under the act.37 This provides for a central
registry and the tracking of which companies or persons
maintain databases of personal information. Data users and
bureaux must demonstrate a need and purpose behind their
possession of personal data.

The act provides tort remedies to any person who is
SION (1970); Balance Between Scientific Freedom and
NAtional Security, 23 JURIMETRICS J. 1
(1982)(current laws and regulations limiting scien-
tific and technical expression exceed the legitimate
needs of national security); Hon. M. Feldman, Why the
First Amendment is not Incompatible with National
1987). Compare Bork, Neutral Principles and Some
First Amendment Problems, 47 IND. L. J. 1 (First
Amendment applies only to political speech); G. Lewy,
Can Democracy Keep Secrets, 26 POLICY REVIEW 17
(1983)(endorsing draconian secrecy laws mirroring the
English system).
33. For example, the NSA has just recently allowed
the Drug Enforcement Agency (DEA) to purchase TEMPEST
Certified computer equipment. The DEA wanted
secure computer equipment because wealthy drug lords
had were using TEMPEST eavesdropping equipment.
34. An Act to regulate the use of automatically
processed information relating to individuals and the
provision of services in respect of such information.
Data Protection Act 1984, Long Title.

June 7, 1990

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damaged by disclosure of the personal data.38 Reasonable
care to prevent the disclosure is a defense.39 English
courts have not yet ruled what level of computer security
measures constitute reasonable care. Considering the
magnitude of invasion possible with TEMPEST ELINT it should
be clear by now that failure to use TEMPEST Certified
equipment is prima facie unreasonable care.

The Remedies section of the act provides incentive for
these entities to provide successful protection of person
data from disclosure or illicit access. Failure to protect
the data will result in monetary loss. This may be looked
at from the economic efficiency viewpoint as allocating the
cost of disclosure the persons most able to bear those
costs, and also most able to prevent disclosure. Data users
that store personal data would use TEMPEST Certified
equipment as part of their computer security plan, thwarting
would-be eavesdroppers.

35. "Personal data" means data consisting of informa-
tion which relates to a living individual who can be
identified from that information (or from that and
other information in the possession of the data user),
including any expression of opinion about the indivi-
dual but not any indication of the intentions of the
data user in respect of that individual.
Data Protection Act 1984 1(3)
36. "Data user" means a person who holds data, and
a persons "Holds" data if --
(a) the data form part of a collection of data pro-
cessed or intended to be processed by or on behalf of
that person as mentioned in subsection (2) above;
[subsection (2) defines "data"] and
(b) that person (either alone or jointly or in common
with other persons) controls the contents and use of
the data comprised in the collection; and
(c) the data are in the form in which they have been
or are intended to be processed as mentioned in para-
graph (a) above or (though not for the time being in
that form) in a form into which they have been con-
verted after being so processed and with a view to
being further so processed on a subsequent occa-
Data Protection Act 1(5).
37. Data Protection Act 1984, 4,5.
38. An individual who is the subject of personal data
held by a data user... and who suffers damage by rea-
son of (1)(c) ... the disclosure of the data, or ac-
cess having been obtained to the data without such
authority as aforesaid shall be entitled to compen-
sation from the data user... for any distress which
the individual has suffered by reason of the ...

June 7, 1990

- 16 -

The Data Protection Act 1984 allocates risk to those who
can bear it best and provides an incentive for them to
keep other individuals' data private. This act should be
adopted by the United States as part of a full-spectrum plan
to combat TEMPEST eavesdropping. Data users are in the best
position to prevent disclosure through proper computer
security. Only by making them liable for failures in

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77777777777security can we begin to rein in TEMPEST ELINT. Do not
criminalize TEMPEST ELINT. Most crimes that TEMPEST ELINT
would aid, such a insider trading, are already illegal; the
current laws are adequate.

- 16 -
777777777The National Institute of Standards and Technology should
immediately begin a program to educate the private sector
about TEMPEST. Only if individuals are aware of the threat
can they take appropriate precautions or decide whether
any precautions are necessary.

- 16 -
7777777777Legislation should be enacted to require all elec-
tronic equipment to prominently display its level of
emanations and whether it is TEMPEST Certified. If
individuals are to choose to protect themselves they must be
able to make a informed decision regarding how much
protection is enough.

- 16 -
77777777777TEMPEST Certified equipment should be available to the
private sector. The current ban on selling to non-
governmental agencies prevents individuals who need to
protect information from having the technology to do so.

- 16 -
777777777Possession of TEMPEST ELINT equipment should not be made
illegal. The inherently passive nature and simple
design of TEMPEST ELINT equipment means that making its
possession illegal will not deter crime; the units can be
easily manufactured and are impossible to detect. Limiting
their availability serves only to monopolize the
countermeasures research, information, and equipment for the
government; this prevents the testing, design and
manufacture of counter-measures by the private sector.

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77777777777777Legislation mirroring England's Data Protection Act 1984
should be enacted. Preventing disclosure of personal data
can only be accomplished by giving those companies hold-
ing the data a reason to protect it. If data users are
held liable for their failure to take reasonable security
precautions they will begin to take reasonable security
precautions, including the use of TEMPEST Certified

9 [] Respectfully submitted,

Christopher J. Seline [email protected]
[email protected]


June 7, 1990

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