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 MIL-HDBK-232A
4.
GENERAL REQUIREMENTS
4.1 General. Section 4 provides minimum engineering-installation guidance
for general application to all equipment and systems processing classified
information, Two interrelated principles apply - the RED/BLACK concept (see
FED-STD-1037) and TEMPEST (see NCSC-9). The RED/BLACK concept provides that
electrical and electronic components, equipment, and systems processing
classified plain text information be kept separate from those that process
encrypted or unclassified information. TEMPEST, as used here, is those
measures used to control compromising emanations. Figure I depicts a
facility designed to RED/BLACK and TEMPEST guidance.
While these terms are
often used interchangeably, the concepts are separate and distinct. A
facility properly designed to provide RED/BLACK separation may contain
TEMPEST discrepancies. The guidance of this handbook presupposes the use of
low-level balanced voltage digital signaling as defined in MIL-STD-188-114
and NACSIM 5002, except where specifically noted otherwise (e.g., unbalanced
voltage digital signaling). Additional treatments may be required for all or
part of a facility if high-level signaling is used. TEMPEST testing after
installation and activation may indicate the need for additional protective
measures. Such additional treatment will be determined by the cognizant
TEMPEST authority on a case-by-case basis. Consideration will also be given
to TEMPEST benefits derived from protection for electromagnetic pulse
(EMP)/high-altitude electromagnetic pulse (HEMP), electromagnetic
interference (EMI), and radio frequency interference (RFI). Although this
handbook is not specifically directed to the measures used for EMP/HEMP
protection, the attributes of EMP protection which may satisfy TEMPEST have
been addressed (see appendix C). The design considerations of EMP and
TEMPEST are similar - to protect signals and equipment in one area from
activity in another area. The major differences are in the levels (voltage,
current, and field strength, which are very high for EMP/HEMP signals and
normally moderate to quite low for TEMPEST signals), and the direction of
protection (outside to inside for EMP/HEMP and inside to outside for
TEMPEST). The major differences in practices used to provide both types of
protection are found in treatment of grounding paths and in the amount, and
to some extent, the types of protection provided for any paths that are
required between outside and inside. In general, any facility that is
adequately protected from EMP/HEMP effects will provide a significant portion
of the required TEMPEST protection. The requirements for effective RFI/EMI
control are similar to those for EMP/HEMP and TEMPEST. RFI and EMI can be
either external (keep it out) or internal (keep it from getting out). The
practices to accomplish this containment are defined in electromagnetic
compatibility (EMC) programs. The practices used to control each are very
closely related to those for TEMPEST and EMP/HEMP. This handbook will
provide the minimum guidance required for RED/BLACK installations. This
guidance, where applicable, will track with practices required for control of
RFI/EMI or EMP/HEMP effects. Six major design and installation techniques
are used in the RED/BLACK environment.
a.
Grounding.
d.
Physical separation.
b.
e.
Physical protection.
c.
Shielding.
f.
Filtering and isolation.
These techniques will be used in varying degrees in every installation that
processes classified information.
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