Editing Tempest (codename) (section)

==Shielding standards==
Many specifics of the TEMPEST standards are [[classified information|classified]], but some elements are public. Current United States and [[NATO]] Tempest standards define three levels of protection requirements:<ref>{{cite web |url=http://www.sst.ws/tempest_standards.php |title=SST: TEMPEST Standards SDIP 27 Level A, Level B & AMSG 784, 720B, 788A |publisher=Sst.ws |access-date=2015-05-31}}</ref>
*'''NATO SDIP-27 Level A''' (formerly AMSG 720B) and '''USA NSTISSAM Level I'''
:''"Compromising Emanations Laboratory Test Standard"''
:This is the strictest standard for devices that will be operated in ''NATO Zone 0'' environments, where it is assumed that an attacker has almost immediate access (e.g. neighbouring room, 1 metre; 3' distance).
*'''NATO SDIP-27 Level B''' (formerly AMSG 788A) and '''USA NSTISSAM Level II'''
:''"Laboratory Test Standard for Protected Facility Equipment"''
:This is a slightly relaxed standard for devices that are operated in ''NATO Zone 1'' environments, where it is assumed that an attacker cannot get closer than about {{convert|20|m|ft}} (or where building materials ensure an attenuation equivalent to the free-space attenuation of this distance).
*'''NATO SDIP-27 Level C''' (formerly AMSG 784) and '''USA NSTISSAM Level III'''
:''"Laboratory Test Standard for Tactical Mobile Equipment/Systems"''
:An even more relaxed standard for devices operated in ''NATO Zone 2'' environments, where attackers have to deal with the equivalent of {{convert|100|m|ft}} of free-space attenuation (or equivalent attenuation through building materials).

Additional standards include:
*'''NATO SDIP-29''' (formerly AMSG 719G)
:''"Installation of Electrical Equipment for the Processing of Classified Information"''
:This standard defines installation requirements, for example in respect to grounding and cable distances.
*'''AMSG 799B'''
:''"NATO Zoning Procedures"''
:Defines an attenuation measurement procedure, according to which individual rooms within a security perimeter can be classified into Zone 0, Zone 1, Zone 2, or Zone 3, which then determines what shielding test standard is required for equipment that processes secret data in these rooms.

The NSA and Department of Defense have declassified some TEMPEST elements after [[Freedom of Information Act (United States)|Freedom of Information Act]] requests, but the documents black out many key values and descriptions. The declassified version of the TEMPEST test standard is heavily [[sanitization (classified information)|redacted]], with emanation limits and test procedures blacked out.{{citation needed|date=March 2017}}<ref>{{Cite journal|last=Ulaş, Cihan, Serhat Şahin, Emir Memişoğlu, Ulaş Aşık, Cantürk Karadeniz, Bilal Kılıç, and Uğur Saraç|title=Development of an automatic TEMPEST test and analysis system|journal=Scientific Cooperations International Workshops on Electrical and Computer Engineering Subfields}}</ref> A redacted version of the introductory Tempest handbook NACSIM 5000 was publicly released in December 2000. Additionally, the current [[NATO]] standard SDIP-27 (before 2006 known as AMSG 720B, AMSG 788A, and AMSG 784) is still classified.

[[File:TEMPEST Shielding Requirements.png|thumb|TEMPEST Shielding Requirements]]
Despite this, some declassified documents give information on the shielding required by TEMPEST standards. For example, Military Handbook 1195 includes the chart at the right, showing electromagnetic shielding requirements at different frequencies. A declassified NSA specification for shielded enclosures offers similar shielding values, requiring, "a minimum of 100 dB insertion loss from 1&nbsp;kHz to 10&nbsp;GHz."<ref>{{Citation |title= Specification nsa no. 94-106 national security agency specification for shielded enclosures |url= http://cryptome.info/0001/nsa-94-106.htm |publisher=Cryptome.info |access-date= 2014-01-28 }}</ref> Since much of the current requirements are still classified, there are no publicly available correlations between this 100&nbsp;dB shielding requirement and the newer zone-based shielding standards.

In addition, many separation distance requirements and other elements are provided by the declassified NSA [[red/black concept|red-black]] installation guidance, NSTISSAM TEMPEST/2-95.<ref>{{Citation |title= NSTISSAM TEMPEST/2-95 RED/BLACK INSTALLATION |url= http://cryptome.org/tempest-2-95.htm |author= N.S.A. |publisher=Cryptome.org |access-date= 2014-01-28 }}</ref>