Tempest (codename)

Tempest (codename)

Tempest (often spelled TEMPEST) is a codename referring to investigations and studies of compromising emanations (CE) (see Van Eck phreaking). Compromising emanations are defined as unintentional intelligence-bearing signals which, if intercepted and analyzed, may disclose the information transmitted, received, handled, or otherwise processed by any information-processing equipment.

Compromising emanations consist of electrical, mechanical, or acoustical energy intentionally or by mishap unintentionally emitted by any number of sources within equipment/systems which process national security information. This energy may relate to the original encrypted message, or information being processed, in such a way that it can lead to recovery of the plaintext. Laboratory and field tests have established that such CE can be propagated through space and along nearby conductors. The interception/propagation ranges and analysis of such emanations are affected by a variety of factors, e.g., the functional design of the information processing equipment; system/equipment installation; and, environmental conditions related to physical security and ambient noise. The term "compromising emanations" rather than "radiation" is used because the compromising signals can, and do, exist in several forms such as magnetic- and/or electric field radiation, line conduction, or acoustic emissions.

The term "Tempest" is often used broadly for the entire field of emission security or emanations security (EMSEC). The term "Tempest" was coined in the late 1960s and early 1970s as a codename for the National Security Agency operation to secure electronic communications equipment from potential eavesdroppers and vice versa the ability to intercept and interpret those signals from other sources.

The U.S. government has stated that the term TEMPEST is not an acronym and does not have any particular meaning. However, various backronyms have been suggested, including "Transmitted Electro-Magnetic Pulse / Energy Standards & Testing", "Telecommunications ElectroMagnetic Protection, Equipment, Standards & Techniques", "Transient ElectroMagnetic Pulse Emanation STandard", and "Telecommunications Electronics Material Protected from Emanating Spurious Transmissions". As a joke - but just as factually possible as other attempts - the phrase "Tiny ElectroMagnetic Particles Emitting Secret Things" has been suggested.