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Compromising emanations (codename) - this page is a stub

TEMPEST is an NSA specification and a NATO certification, referring to spying on information systems through leaking emanations. This includes the emission of unintentional intelligence-bearing signals, such as Radio Frequency (RF) signals, light and acoustic vibrations [1]. If such signals are intercepted and analysed by an adversary (side-channel attack), they might disclose sensitive information. In cryptography, this might lead to reconstruction of (part of) the plaintext.

In practice, TEMPEST covers methods to spy upon others, as well as methods to shield equipment against such spying by others. The latter is also known as Emission Security (EMSEC), which is a subset of Communications Security (COMSEC). Protecting equipment against TEMPEST-based spying is done by means of distance, shielding, filtering and masking. Equipment to check a device for unwanted emanations, is part of Technical Surveillance and Counter-Measures (TSCM).

TEMPEST countermeasures on this website
RF leak detector for shielded enclosures
Examples of TEMPEST-shielded equipment
TEMPEST power supply unit for Fialka cipher machine
Spendex-40 secure telephone for voice, fax and computer
Spendex 50 (DBT), military secure crypto phone
CIS Secure DTD-7962-T2 TEMPEST version of Cisco 7962G Unified IP Phone
TEMPEST affected equipment
KL-7 rotor-based cipher machine (USA)
Ecolex II, developed by PTT, manufactured by Philips Usfa
In the US, the presence of unwanted emanations was first discovered – accidentally – by Bell Labs engineers in 1943. Whilst using a 131-B2 (PYTHON) One-Time Tape (OTT) cipher machine, one of the engineers noticed glitches (spikes) on his oscilloscope that was at a considerable distance from the machine. It appeared that the relays of the connected teletype equipment caused the radiation of Radio Frequency (RF) signals, and that since the five relays that represented in the input character were not operated simultaneously, the plaintext character could be reconstructed.

Recognised TEMPEST phenomena:

  1. RF Radiation
  2. Induction/Conduction
  3. Magnetic fields
  4. Power line modulation
  5. Acoustics
  6. Seismics
  • Shielding
  • Filtering
  • Masking
  1. Wikipedia, Tempest (codename)
    Retrieved 29 August 2021.

  2. NSA, TEMPEST: A Signal Problem 1
    The story of the discovery of various compromising radiations
    from communications and Comsec equipment.

    NSA Cryptologic Spectrum, Summer 1972 - Vol. 2, No. 3. pp. 26-30. SECRET
  1. Partly approved for release by NSA on 29 September 2007. FOIA Case # 51633.

Further information
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Crypto Museum. Created: Sunday 29 August 2021. Last changed: Monday, 15 April 2024 - 06:03 CET.
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