Schneier on Security

Clive Robinson • October 28, 2010 12:57 PM

First on a historic note in the early 1940’s the US where bugging everybody the UK included.

Unofficialy all telex companies where supplying copies of all telex’s they carried to the US agencies (this has been documented many times before).

One of the early TEMPEST “war stories” is about the UK Rockex One Time Tape online cipher equipment. It turns out that not only could you strip away the OTT from the plain text by observing the signals on the telex line but also by the sounds the equipment made (Post Office 600 relays make a distinctive clicking noise). It was also later shown that the long PSU leads also radiated a signal that could also be used to strip the OTT. The US informed the UK F&CO staff about this over concernce that data sent back over the UK Diplomatic channel was leaking to amongst others the Russians.

Solving the Rockex’s problems fell to a Canadian electrical enginering professor, there are some minutes from UK “Ccabinate Office” memos that provide some details.

@ Tangerine Blue,

“I care less about spying on foreign embassies suspected of subterfuge, than about spying on American civilians who are suspected of nothing.”

Effectivly they have been doing it since before the end of WWII. What has changed is they nolonger “out source” it via the likes of the UK to avoid having to lie to the US people.

When Britain under BRUSA (later UKUSA) agrement spied on US citizens for the US, members of the various US Intel three leter agencies could stand infront of various US house commities and honestly say “The XXX does not spy on US citizens” because it was sort of true the British did it for them and likewise the US did it for Britain. Later BRUSA included nearly all the WASP nations in the cosy little deal.

All the Bush administration did was bring it “back in house” and ramp up the funding to make it that much more pervasive.

Clive Robinson • October 28, 2010 4:43 PM

@ NobbodySpecial,

“I think you would have to be pretty naive to assume it wasn’t. Of all the things you could accuse the Japanese military of in 1940 I don’ think naiveté was one of them.”

I was actually asking if there was documentry evidence for the assumption, as other historical documentation sugests otherwise.

But as it happens the Japanese where not particularly adept at certain types of engineering at the time of WWII. Although they had certainly come along a great deal from the “Great War”, But as the Battle of Medway showed they could be very naive at times (the Japanese Admiral alowing the pilots to have a meal rather than go back to check they had actually dealt with all the US carrriers).

As for “bugging” you have to remember the state of the art in sensitive microphones at that time was the “ribbon mic” these where fairly large and quite fragile and needed almost constant adjustment. The most common and robust microphone of the 1940’s era was still the “carbon granual” telephone microphone it was fairly easy to interface to the likes of valve based transmitter circuits (in the cathode circuit). But it was fairly insensitve and would have required a lot of amplification to be used for bugging a room and valve amps in 1940 where not exactly small, the all glass pressed based acorn valve was only perfected in 1939 which later became the famous EF50 used in 200MHz radar and it was quite big. It was not untill after 1940 that the miniture or thumb nail acorn valves where developed. This lack of small amplifier or long microphone cable would have made both noise and sensitivity quite an issue.

The newish (for then) replacment for the carbon granual microphone was the diaphragm induction microphone, however this was quite low impeadance and did not come into it’s own for a number of years, and in the early designs it was about as sensitive as the carbon granual microphone (it became better as the design of the diaphragm improved).

As for “bugs” in the sense we know them today they where invented in New York by the mafia back in the early 1960’s and used the likes of the OC71 germanium transistor and were a follow on from the harmonica or hook switch bug. The mafia actually used them against the police and FBI quite successfully for a number of years.

The harmonica bug was an electromechanical device consisting of a “reed actuator” and a small relay. when the correct tone was played down the line the reed actuator responded and pulled in the relay. One set of relay contacts where across the hook switch the other across the reed actuator so that when the relay had “pulled in” it remained held. The way to “kill” the harmonica bug was to dial a number the rotary dial put a short directly across the telephone pair, thus with no power to hold the relay in it droped out. In some of the better informed spy and crime thrillers you would see the “hero” dial a couple of numbers and then jam a pencil or some such into the rotary dial to hold the dial switch closed thus putting a dead short on the whole phone.