Editing Acoustic cryptanalysis (section)

== History ==
[[Victor Marchetti]] and [[John D. Marks]] eventually negotiated the declassification of CIA acoustic intercepts of the sounds of cleartext printing from encryption machines.<ref>{{Cite book|title=[[The CIA and the Cult of Intelligence]]|last1=Marchetti|first1=Victor|last2=Marks|first2=John|date=1974|publisher=Knopf|isbn=0394482395}}</ref> Technically this method of attack dates to the time of [[Fast Fourier transform|FFT]] hardware being cheap enough to perform the task; in this case the late 1960s to mid-1970s. However, using other more primitive means such acoustical attacks were made in the mid-1950s.

In his book ''[[Spycatcher]]'', former [[MI5]] operative [[Peter Wright (MI5 officer)|Peter Wright]] discusses use of an acoustic attack against [[Egypt]]ian [[Boris Hagelin|Hagelin]] cipher machines in 1956. The attack was [[codename]]d "ENGULF".<ref name=Spycatcher>{{citation
 | title = Spycatcher: The candid autobiography of a senior intelligence officer
 | first1=Peter | last1=Wright | author-link = Peter Wright (MI5 officer)
 | year = 1987
 | publisher = Viking}}</ref>