THE KL7 OFF-LINE CRYPTO UNIT
                      by Jerry Proc VE3FAB
                    Email: jproc@worldlinx.com  

     The KL7 was an 'off-line' cipher machine, code name ADONIS,
and was similar to, but more advanced than the famous German Enigma
machine. The story which follows, outlines the use of the KL7 in a
naval environment. 

     Mechanically, the unit had the approximate dimensions of a
medium sized portable typewriter and was housed in an extruded
aluminum carrying case which was painted in an olive drab, khaki
colour. Navy versions, were of course, navy grey and the case lid
opened from front to rear. The KL7 was a five rotor system with a
wiring maze in each rotor and a supplemented with an operators
plugboard. Standard power was obtained from a 120 volt 60 Hertz
source. Cryptovariables such as rotor and plugboard settings were
referenced from a hard bound paper code book or 'flash' paper bound
into a small booklet. 

     To encrypt a plain text message, the crypto operator would
enter the message on the keyboard and the KL7 generated a gummed
tape using 5 letter groups. The tape was pasted on a message pad
where specific information such as Routing Indicators and a Date-
Time-Group was added. Finally, the complete message was passed to
a radio or a Teletype operator for transmission. To decrypt, coded
messages were received in 5 letter groups. These, in turn, would be
entered on the KL7 keyboard, and the machine would generate a
gummed tape with the plain language text on it. This was pasted on
a message pad and where it was typed up and duplicated for
distribution within the ship and for filing. According to Walt
Hutchens, an ex-USN coder, "the noise produced by the KL7 rotors
advancing was one of the two most distinctive sounds that I have
ever heard. The other sound was the last round and the clip being
ejected from an M-1 Garand". 

     Components for the KL7 and its variants were manufactured in
the mid 50's to the mid 60's by several United States government
contracted firms and the Singer Company was a major supplier. The
parts were then assembled at either the Philadelphia Army Depot or
at the Bluegrass, Kentucky plant. After final assembly, the units
became the property of the National Security Agency and were
distributed to the various military users. All crypto machines and
materials were on loan to North Atlantic Treaty Organization member
countries including Canada. In addition, there was also an airborne
version of the KL7 which was modified at one of the US Air Force
Security Service facilities in Mississippi for use in aircraft.

     The KL7A was a battery powered version which had a higher
degree of soundproofing to counter the problems produced by the
acoustics of the machine. Batteries were not intended for
portability, but for technical security reasons. Since the machine
had a high TEMPEST and acoustical signature, there were concerns
that it might be 'exploitable'. TEMPEST is an unclassified term
that describes the vulnerability of an electronic device to having
the classified components of its design intercepted and exploited.
A machine that does not process classified information does not
have a TEMPEST problem, only a radio frequency interference
problem. Acoustical signature describes those systems which make an
audible sound (sonic or subsonic or ultrasonic) which is repetitive
and identifiable to certain specific functions. If these sounds are
recorded from a distance, it is potentially feasible to compromise
the machine.      

     After the Walker family spy ring was exposed in the mid
1980's, it was found that they had supplied the Soviet Union with
a complete working KL7 and all keying materials. Immediately, all
KL7's were withdrawn from service and returned to the NSA's COMSEC
depot at Ft. Mead Maryland. This included all code books, spare
parts, manuals and any other paraphernalia associated with the
unit.  

     Another crypto system known by the code name of Orestes
employed a device called the KW7. The KW7 was an on-line,
send/receive crypto unit installed in shore stations and aboard
ships. It was used for ship to shore and for intership
radioteletype communications. To send messages over a secure UHF
teletype circuit, a model 28 Teletype or reader (T-D) sent the
prepared message to the KW7, which in turn, controlled a UHF
transmitter in the AM mode. Note, that the KW7 was not a
synchronous unit, therefore, it required a phasing signal to be
sent in order to attain a lock on the received signal. 

     All of the KL7 crypto units fitted aboard ships was owned by
the National Security Agency of the United States and was also
loaned to North Atlantic Treaty Organization member countries
including Canada. Also included, was keying material, key lists,
rotors, and key cards. This material came in a variety of editions
depending upon the application. Some versions of these packages
would be named CANUSEYESONLY (Canadian user eyes only), CANUKUS
(for Canada/UK and US), AUSCANUKUS (for Australia, Canada, the US
and the UK), NATO, ALLIED, and so on. 

     It is interesting to note that by 1969 standards, the life
cycle of a crypto system was generally set at 20 years even if the
hardware didn't wear out. The KL7 system was still in use in 1969,
long after its life expiry cycle. When crypto equipment was deemed
surplus or obsolete, it was destroyed. Ships not equipped with on-
line crypto equipment were considered to have a distinct time
disadvantage in ship-shore-ship and inter-ship operations. 

     Many thanks go to Cdr. Bob Willson (RCN, Ret'd) of HMCS Haida,
Lt. Cdr Frank Dunbar (RCN, Ret'd), David Mann of the British
West Indies and Walt Hutchens for supplying the source material.   
--EOF--