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KL-7   ADONIS, POLLUX
Rotor-based off-line cipher machine

KL-7 was an electro-mechanical rotor-based off-line cipher machine, developed in 1952 by the US National Security Agency (NSA) as a replacement for the wartime SIGABA (ECM Mark II) and in some countries, such as the UK and Canada, also as a replacement for the CCM and the Typex. The machine was initially known as AFSAM-7, but was renamed TSEC/KL-7 in the early 1960s.

The machine is also known by the codenames of the key procedures: POLLUX for low-level traffic and ADONIS for high-level traffic. Unlike its predecessors, the KL-7 has 8 electrical rotors, 7 of which move in an irregular stepping pattern when enciphering. The remaining rotor is static.

The rotors are held in a removable drum. Each rotor has 36 contact points at either side, which is more than the 26 letters of the Latin alphabet that can be encrypted. The remaining 10 lines are looped back to the input, using a patented technique known as re-entry or re-injection.
  
KL-7 in transit case

The KL-7 was used by the US Army, the US Navy, the US Air Force, and by NATO. It was also used by the Foreign Office of several NATO countries — including the US — for diplomatic traffic. The machine was introduced in 1952 and remained in service well into the 1970s, after which it was gradually phased out. In some countries, KL-7 machines were kept for special purposes and as backups for many years, until they finally were officially withdrawn from service in 1983. The last (unclassified) message was sent on 30 June 1983 by the Canadian Navy. KL-7 was replaced by a range of electronic machines, including the KW-26, KW-37, KL-51 (RACE) and Aroflex.

The security of the KL-7 was compromised by several people, the most notorious of which was probably John Walker, who suplied the key lists of the KL-7 (and other machines) to the Russians for nearly 17 years. Nevertheless, the machine remained classified for nearly 40 years after it was decommissioned. Over time however, researchers were able to reconstruct the machine, resulting in a several accurate computer simulations. The machine was finally declassified in March 2021.

KL-7 with transit case and maintenance kit
KL-7 in transit case
KL-7 outside the transport case
KL-7 outside the transport case
Rotor drum seen from the front right
Rotor drum seen from the bottom
Kl-7 drum with end plate and 8 rotors
Right and left side of a KL-7 rotor
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KL-7 with transit case and maintenance kit
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KL-7 in transit case
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KL-7 outside the transport case
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KL-7 outside the transport case
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Rotor drum seen from the front right
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Rotor drum seen from the bottom
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Kl-7 drum with end plate and 8 rotors
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Right and left side of a KL-7 rotor

Features
The KL-7 is supplied in a green transit case from within which it can be operated. It has a water­tight lid that is held in place by six strong snap locks. Once removed, the lid can be attached to the side of the case with two twist locks, as shown in the image below. In this position it can be used as a copy holder for a paper sheet and or a paper strip. Power cable, work light and a spare ink ribbon are stowed inside the lid. Further tools and spare parts are supplied in a separate box.

KL-7 in transit case, with case lid fitted on top

To operate the machine, it should be pulled forward, so that the keyboard sticks out somewhat. A wide metal locking spring at the bottom of the case, prevents the machine from falling out. It can be removed from the transit case, by pushing the locking spring down, and pulling the machine out completely. This is necessary when the rotor drum has to be removed and for maintenance.

The image below shows the bare machine after it has been removed from the transit case. It is build on a metal chassis (KLB-7) and has two frames at the sides that allow it to be moved in and out of the transit case, like the drawer of a desk. At the front is the keyboard with the 4-position mode selector to its left. Immediately behind the keyboard are the printer and the stepping unit.

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The stepping unit acts as a bay for the rotor drum, which is held in place by two locking levers. This allows the rotor drum to be swapped quickly when the cryptographic KEYs were changed at midnight. At the front edge of the stepping unit are 7 push-buttons that allow each of the seven movable rotors to be stepped to the desired position, using the horizontal white line as an index. The stepping unit and the drum were the only KL-7 items that were classified until March 2021.

The complete timing of the machine is controlled by a gearbox that is fitted at the left side, just behind the printer. It drives the stepping unit, the printer and the electronic circuits, and is also responsible for generating the 400V AC power for the valves (tubes). The machine should be powered by an external 24V DC power supply, such as the battery of a truck or a mains PSU.

Mode selector
The MODE-selector, fitted to the left of the keyboard, offers the following settings:

  • O
    Off
  • P
    Plain
  • E
    Encrypt
  • D
    Decrypt
In Plain-mode (P), all characters are printed directly to paper. When encrypting (E), the keys for FIG, LET and SPACE are mapped to J, V and Z respectively, whilst J is mapped to Y and Z to X, as described further down this page. When decrypting (D), the input and output contacts of the drum are swapped, and the above described letter mapping is reversed (with some restrictions).

KL-7 inside transit case, with lid fitted on top
KL-7 inside transit case, with lid fitted on top
KL-7 in transit case
KL-7 in transit case
Twist lock to fixate the case lid
Inside the top lid
Work light
Work light
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KL-7 inside transit case, with lid fitted on top
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KL-7 inside transit case, with lid fitted on top
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KL-7 in transit case
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KL-7 in transit case
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Twist lock to fixate the case lid
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Inside the top lid
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Work light
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Work light

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Parts
Transit case
KLB-7 base unit
KLA-7 stepping unit
Removable rotor drum with 9 rotors
Electrical cipher wheels, or rotors, with 36 contact points each
Non-movable rotor, wired only by the NSA
Work light
Power cable for 24V DC
Box with tools, supplies and spare parts
Mains power supply unit (24V DC)
PSU
KLX-7 teleprinter interface
EZ-KL7 tandem unit (for error checking)
Transit case
The KL-7 is normally stowed in the green fibre transit case 1 shown in the image on the right, which is known as the Carrying Case Assembly. It can be operated from within this case. After removing the lid (held in place by 6 strong snap locks) the front of the machine becomes visible.

After pulling the machine half-way out, it can be operated from within the carrying case. Power must be supplied to the short flying lead to the right of the keyboard. When unused, the power connector is stowed in a dummy socket.
  
Transit case

  1. There was a similar fibre case in which the accessories, the maintenance kit and the AC mains power supply unit were stowed. For office use, the machine was generally supplied in a non-waterproof aluminium case with a hinged cover that doubles as a copy holder.

Base unit   KLB-7
The base unit of the machine is shown in the image on the right. It is known as KLB-7 and consists of a metal base on which the keyboard, the printer, the motor, the gearbox and the valve-based electronics are fitted permanently.

At the side are two frames that allow it to be fitted inside the transit case, sliding in and out like the drawer of a desk.

 More information

  
KLB-7: KL-7 with rotor drum and stepping unit removed

Stepping unit   KLA-7
The KLA-7 stepping unit – shown in the image on the right – is fitted in the rear right corner of the KL-7, and connects to the KLB-7 base unit by means of a series of spring loaded contacts. It is held in place by two metal clamps at the rear and two hand-operable screws at the front.

The stepping unit acts as a bay for the rotor drum and is responsible for the stepping motion of the seven movable rotors. In February 2011, Crypto Museum revealed the operating principle of the stepping unit. Until March 2021, the KLA-7 stepping unit was a classified item.

 Technical details

  
Stepping unit - seen from the front right

Rotor drum   KLK-7
At the heart of the KL-7 are eight cipher wheels. Seven of these are movable under control of the stepping unit. They are marked A thru K. 1 The 12th rotor is a static one. It is marked with the letter 'L' and is always fitted in position 4.

The rotors are mounted on a spindle inside the cylindrical basket shown in the image on the right. The complete assembly is known as the drum. The right end-plate of the drum is removable. At the bottom are 36 contacts at either side, that mate with two sets of 10 spring-loaded contacts on the stepping unit and two sets of 26 contacts at the KLB-7 base unit.

 More information

  
Rotor drum seen from the front right

  1. A total set of 11 movable rotors (A-K) was supplied, 7 of which were placed in the machine.

Moving rotors   KAR-x
Inside the rotor drum are eight electrical cipher wheels, or rotors, seven of which are movable. Each rotor has 36 flat-faced contacts at its left side, and 36 spring-loaded contacts at its right side. The contacts at the left are wired to the contacts at the right in a secret scrambled order.

The movable rotors are marked A to K 1 and have a white index ring with notches and lugs, that can be pressed and turned. The wiring of these wheels was different for each group of users, and was changed regularly.

 More information

  
Right and left side of a KL-7 rotor

  1. A total set of 11 movable rotors (A-K) was supplied, 7 of which were placed in the machine.

Fixed rotor
In addition to the seven movable rotors, there was one fixed rotor that was installed in the drum in position four (between rotors three and five). It has two differently sized keying lugs at its circumference, to ensure that it could only be installed in one orientation. This rotor is also known as the stationary wide rotor.

Any movable rotor can be converted into a stationary wide rotor, by removing the white notched ring and replacing it by the wide metal one. In the setup shown here, the fixed rotor is marked with the letter 'L', and was rewrired by the NSA only; never by the using organisation.

 More information

  
L-rotor

Work light
When operating the machine in the dark, it could be useful to use the reading light shown in the image on the right. The lamp, that is normally stowed inside the top lid of the transit case, can be installed in a fitting just behind the keyboard. It has a gooseneck between the connector and the head, allowing it to be adjusted easily.

At the front of the head are two polaroid filters, of which the frontmost one can be turned. This allows the light to be dimmed as desired.
  
Work light

Power cable
The KL-7 should be powered by an external 24V DC source, such as the battery of a (military) vehicle or a truck. For this purpose, the rubber power cable shown in the image on the right was supplied with the machine. When unused it was stowed inside the case lid.

When used in an office environment, an external mains power supply unit (PSU) was used.

 Plug wiring

  
Power cable

Maintenance kit
For regular maintenance, the small metal case shown in the image on the right was available. It has a hinged lid and contains a selection of tools, spare parts (tubes), contact cleaning aids and a water dispenser for gummed paper tape.

The box has two slots at the bottom rear corners, and two hand-operable screws in the front corners, so that it could be mounted onto a maintenance frame, together with the PSU. This frame had roughly the same size as a KL-7, so that it could be stowed in a KL-7 transit case.

 More information

  
KL-7 Operator Maintenance Kit

Power supply unit
When used in a stationary environment, such as an office, the KL-7 was usually powered by the external power supply unit (PSU) shown here. If necessary it could be bolted to the table using the four threaded holes at the corners.

The PSU is suitable for connection to the 110V or 220V AC 50 or 60 Hz mains network, selectable with the voltage selector at the top. The example at the right is configured for 220-250V AC as used throughout Europe. The device does not have an ON/OFF switch.

  
KL-7 power supply unit

Teleprinter interface   KLX-7
In its basic configuration, the KL-7 is suitable for offline use only. Encrypted text is printed on the built-in paper strip printer, and has to be retyped on a teleprinter for transmission.

As this is a time consuming and error-prone operation, an interface was developed that could (optionally) be installed inside the KL-7, behind the rotor drum. It required a modification to be installed between the keyboard and the base.

 More information

  
Click to see more

Tandem unit   EZ-KL7
The KL-7 had many problems with its spring-loaded contacts, that had to be cleaned regularly with prescribed materials only. The German Army (Bundeswehr) found it so unreliable, that they developed the EZ-KL7 expansion unit.

This unit allows two indentically configured KL-7 machines to be operated in parallel (tandem), and compare their outputs, so that errors could be detected immediately. It is fitted in front of the keyboard and requires the KLX-7 option.

 More information

  
Click to see more

Transit case
Carrying handle and serial number tag
Inside the top lid
Copy holder
KLB-7: KL-7 with rotor drum and stepping unit removed
KL-7 with rotor drum and stepping unit removed
Stepping unit - seen from the front right
Stepping unit - seen from the front left
Stepping unit - front view
10 spring-loaded contacts at the right side of the stepping unit
Close-up of the stepping levers of the stepping unit
Stepping unit - rear view
Stepping unit - bottom side
Rotor drum seen from the front right
Rotor drum seen from the front left
Rotor drum seen from the front
Rotor drum seen from the bottom
Kl-7 drum with end plate and 8 rotors
Empty rotor drum with end-plate removed
Looking into the empty rotor drum
End-plate
Rotor drum with the end-plate removed
Rightmost rotor inside the rotor drum
Right and left side of a KL-7 rotor
L-rotor
L-rotor - right side
L-rotor - left side
L-rotor
L-rotor detail
Keying notch on the L-rotor
Work light
Work light
Polaroid filters
KL-7 work work light
Work light installed in the fitting behind the keyboard
Power cable
Power connector
 KL-7 Operator Maintenance Kit
KL-7 Operator Maintenance Kit
Contents of the maintenance kit
KL-7 power supply unit
KL-7 power supply unit - rear view
KL-7 power supply unit, with power cables stowed
KL-7 power supply unit with power cables
Top with serial number tag and voltage selector
Interior
Interior
Selenium rectifier bridge and wiring detail
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Transit case
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Carrying handle and serial number tag
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Inside the top lid
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Copy holder
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KLB-7: KL-7 with rotor drum and stepping unit removed
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KL-7 with rotor drum and stepping unit removed
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Stepping unit - seen from the front right
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Stepping unit - seen from the front left
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Stepping unit - front view
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10 spring-loaded contacts at the right side of the stepping unit
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Close-up of the stepping levers of the stepping unit
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Stepping unit - rear view
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Stepping unit - bottom side
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Rotor drum seen from the front right
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Rotor drum seen from the front left
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Rotor drum seen from the front
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Rotor drum seen from the bottom
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Kl-7 drum with end plate and 8 rotors
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Empty rotor drum with end-plate removed
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Looking into the empty rotor drum
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End-plate
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Rotor drum with the end-plate removed
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Rightmost rotor inside the rotor drum
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Right and left side of a KL-7 rotor
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L-rotor
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L-rotor - right side
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L-rotor - left side
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L-rotor
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L-rotor detail
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Keying notch on the L-rotor
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Work light
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Work light
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Polaroid filters
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KL-7 work work light
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Work light installed in the fitting behind the keyboard
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Power cable
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Power connector
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 KL-7 Operator Maintenance Kit
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KL-7 Operator Maintenance Kit
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Contents of the maintenance kit
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KL-7 power supply unit
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KL-7 power supply unit - rear view
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KL-7 power supply unit, with power cables stowed
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KL-7 power supply unit with power cables
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Top with serial number tag and voltage selector
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Interior
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Interior
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Selenium rectifier bridge and wiring detail

Block diagram
The KL-7 is an electromechanical rotor-based cipher machine driven by electronic circuits with thermionic valves (vacuum tubes). The machine is powered by an external 24V DC source, such as the battery of a truck or a mains PSU. The complex timing of the machine is controlled by a gear box in which several rotating parts are coupled to a common axle. The block diagram below shows how the various parts interact. The unit is driven by a 24V motor that runs at 6600 RPM. It drives the mechanical parts as well a an AC generator that provides the 400V for the valves.

TSEC/KL-7 Block Diagram

Pressing a key on the keyboard, grounds one of 26 lines, which is then is routed via the mode-selector, through the coding wheels, to one of the 37 coils of the pulse generator. These pulses are used to drive the printer. The rotating parts — DC motor, AC generator, pulse generator, printer and timing unit — are shown in red in the diagram above. As these parts are all axis-coupled, system timing is guaranteed. The single-stepping parts are shown in purple.

 Full circuit diagram
 Repair and maintenance instructions


Rotors   KLK-7
The rotors of the KL-7 resemble those of the Enigma and other rotor-based cipher machines. Each rotor has 36 flat-faced contacts on its left side, that are connected to 36 spring-loaded contacts on the right side, in a secret scrambled order. It also has an adjustable letter ring.

Click to see more

There are some significant differences with the Enigma however. First of all, a KL-7 rotor has 36 contacts, whereas an Enigma wheel has 26 contacts. Of the 36 contacts, 26 are used for the encryption of the 26 letters of the alphabet. The remaining 10 contacts are looped back to the input (see below). This results in a re-encipherment of part of the text, which is covered in US Patent 2,984,700 filed by Albert W. Small on 22 September 1944. In addition, the KL-7 has eight wired rotors, whereas the Enigma had only three or four. Seven rotors are movable; one is static.

Another difference, is the absence of a reflector (Umkehrwalze or UKW). When encrypting, one side of the rotor basket is the input and the other side is the output. In decoding mode, all contacts are swapped, so that the output becomes input and vice versa. This has the advantage that on the KL-7 a letter can encipher into itself, which was not the case with Enigma. Swapping of the input and ouput contacts is done by a large double sided sliding panel with silver-plated contacts, that is integrated with the keyboard. It is controlled by the MODE-selector.



Rotor set   KAR-x
Each KL-7 came with 12 wired rotors 1 marked A to L. Subject to the current cipher instructions, eight of these rotors were placed in the machine. Of these eight rotors, seven were movable and one was static. The unused rotors were stowed in a metal container. With the 12 wired rotors came a set of 11 white plastic notch rings (marked 1 to 11), plus a metal one without notches.

The notch rings control the irregular stepping of the rotors. Subject to the cipher instructions, 7 of the notch rings were fitted to 7 of the selected rotors. The remaining rotor was fitted with the wide metal ring and was always used in position 4 of the drum. This rotor never moves (static).

  1. The set was later expanded with a 13th rotor that was marked 'M', and an extra notch ring marked '12'.

Letter rings
Each wheel has a letter ring with 36 positions, each separated by a narrow gap. Only 26 of these positions are marked with one of the letters of the Latin alphabet (A-Z) in white. The remaining ten positions are unmarked (blank). At the side of the rotor, these positions are marked in white with the numbers 1 to 36. 'A' corresponds to '1'. When unfolded, the letter-ring looks like this:


The blanks are identified with a '+' sign. E.g.: the space between 'G' and 'H' is identified as 'G+'.

The letter ring can be pressed down and rotated, so that the position of the letters (and numbers) is changed relative to the rotor wiring. The setting of the letter ring was part of the daily key. The current position of the letter ring is identified by the number that lines up with the white arrow at the left side of the rotor. In this example the letter ring is set to position '1' (i.e. the letter 'A').

Notch rings
Each set of 12 KL-7 rotors came with 11 white plastic notched rings that could be fitted to any of the rotors. Together with the stepping unit, these notch rings are responsible for the irregular stepping of the rotors. Each notch ring can be pressed down and rotated, so that its position is changed relative to the rotor wiring, using the arrow and the adjacent black line as index marks. The key list specifies which letter of the letter-ring should be embraced by these index marks [C].

Subject to the cipher instructions, 7 notch rings are fitted to 7 of the rotors that are placed in the drum. The remaining rotor must be fitted with the wide metal ring — so that it becomes static — and must be placed in the 4th position of the drum. This rotor never moves during encipherment. The position of the wide metal ring can also be altered by pressing it down and rotating it, until the desired number lines up with the white arrow. In this example it is set to position '18'.



Rotor drum   KLK-7
The the KL-7 rotor drum – also known as the basket or cage – consists of a metal cylinder with a fixed spindle at the centre. This assembly is known as KLK-7. Eight of the available twelve rotors, are installed on the spindle, subject to the current cipher instructions. The rotor in position 4 is static. It never rotates and hence does not have a window to show its setting. It is also known as the stationary wide rotor. 1 It is fitted with the wide metal ring instead of a white notch ring. In the rotor set shown here, the static rotor is marked with the letter 'L', but in theory any rotor could be converted into a static one by swapping its white notch ring for the wide metal one.


For each of the 7 movable rotors, a window is present through which three successive positions of that rotor are visible. The tick white line at the top, marks the current position of the rotors. The blank positions are identified with the previous letter suffixed by a '+' sign. In the example above, the current setting of the movable rotors is identified as →
R R+ Z W+ O R+ Q
.

The drum can be removed from the machine by releasing two locking levers – one at either side of the drum – after which the drum can be lifted out. Once removed, the rotors can be accessed by removing the rightmost end-plate, which is held in place by a sliding lock. The individual rotors can then be removed from the spindle. The spindle itself is a permanent part of the drum.

  1. According to some former users, the static rotor was also known as the NSA rotor, as only the NSA was allowed to alter its wiring. This conflicts with the known key procedures however.

Rotor drum locking lever
Rotor drum seen from the front right
Rotor drum seen from the front left
Rotor drum seen from the front
Rotor drum seen from the bottom
Kl-7 drum with end plate and 8 rotors
Empty rotor drum with end-plate removed
Looking into the empty rotor drum
End-plate
Rotor drum with the end-plate removed
Rightmost rotor inside the rotor drum
Right and left side of a KL-7 rotor
A-rotor - right side
A-rotor - left side
Index arrow at left side of a rotor
Index arrow at right side of a rotor
Rotor-ring detail
Press-down and turn to alter the ring setting
L-rotor
L-rotor - right side
L-rotor - left side
L-rotor
L-rotor detail
Keying notch on the L-rotor
Enigma rotor (left) aside two KL-7 rotors
KL-7 rotor 'B' with its notch ring set to the letter 'E'
Notch ring set to position 'E'
KL-7 rotor with the fixed (wide) ring set to position 18
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Rotor drum locking lever
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Rotor drum seen from the front right
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Rotor drum seen from the front left
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Rotor drum seen from the front
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Rotor drum seen from the bottom
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Kl-7 drum with end plate and 8 rotors
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Empty rotor drum with end-plate removed
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Looking into the empty rotor drum
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End-plate
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Rotor drum with the end-plate removed
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Rightmost rotor inside the rotor drum
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Right and left side of a KL-7 rotor
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A-rotor - right side
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A-rotor - left side
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Index arrow at left side of a rotor
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Index arrow at right side of a rotor
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Rotor-ring detail
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Press-down and turn to alter the ring setting
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L-rotor
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L-rotor - right side
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L-rotor - left side
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L-rotor
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L-rotor detail
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Keying notch on the L-rotor
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Enigma rotor (left) aside two KL-7 rotors
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KL-7 rotor 'B' with its notch ring set to the letter 'E'
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Notch ring set to position 'E'
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KL-7 rotor with the fixed (wide) ring set to position 18

Re-entry principle
Each wheel has 36 contacts at either side, but only 26 of them are used for the encryption of the 26 letters of the Latin alphabet. The remaining 10 contacts are looped back from the rightmost end-plate to the leftmost one, causing some kind of re-encipherement. This principle is known as re-entry, and was discovered during WWII by Albert W. Small whilst working for the US Army Signal Intelligence Service (ASIS), trying to solve the high-level Japanese diplomatic Purple cipher.

The invention was covered by US Patent 2,984,700 that was filed by Small on 22 September 1944. As the information was considered classified by the US Army, it was filed as a SECRET patent, that was kept under wraps until 16 May 1961. In the meantime, Swedish/Swiss inventor Boris Hagelin had come up with a similar idea, for which he filed a patent on 16 October 1953. Although the existence of Small's earlier (secret) patent should have raised a declaration of interference, it some­how didn't, and Hagelin's patent US 2,802,047 was granted in the US on 6 August 1957.

It was Hagelin's intention to use the re-entry principle for his upcoming HX cipher machine. He had filed the patent in the US in 1953, and it was granted on 6 August 1957. To his surprise, the same patent was refused in Japan. When Hagelin was visited by NSA cryptographer William (Bill) Friedman on 22 September 1957, the latter was shocked when Hagelin showed him the re-entry patent. Friedman was well aware of Small's secret 1940 US patent, but kept it from Hagelin [17].

Although Hagelin claimed that it was entirely his idea, it is quite possible (if not likely) that he got the idea after seing a KL-7 machine in action during the early 1950s, and discussing some of its properties with German chief cryptographer Dr. Erich Huttenhain in Bonn in 1952. The principle of re-entry, or re-injection, was also used in 1956, in the Russian M-125 Fialka cipher machine.

British Singlet   BID/60
The rotors of the KL-7 are identical to those used with the British Singlet (BID/60). It is quite possible that the cipher wheels were a joint US/UK development, or that the Americans allowed the British to use the KL-7 rotors in their own cipher machine. The Singlet wheels were manufactured in the UK.

The British Singlet had 10 cipher wheels (rather than 8) but was reported to be interoperable with the KL-7 by using the same eight wheels plus two dummies (i.e. wired straight through).

 More about Singlet
  
Singlet (BID/60)

Rotor wiring
Each KL-7 wheel contains 36 wires which connect the flat-faced contacts from one side with the spring-loaded contacts at the other side, in a secret scrambled order. The wiring of the KL-7 rotors has always been kept secret, but whether or not this makes sense, remains to be seen.

For security reasons, it was forbidden to trace the wheel wiring of the KL-7. Even technical repair personnel was not allowed to trace each individual contact for a faulty connection. They were only allowed to place the spring-loaded contacts on a conducting (metal) surface and test each flat-faced contact for continuity only. This way, the wiring would not be revealed. Faulty rotors were never opened in the field, but had to be returned to the NSA for repair [11].

If you would happen to find a KL-7 today and trace the rotor wiring, it would not be of much use, as the rotor wiring was different for each group of users. Furthermore, the wiring was changed frequently for safety reasons. Nevertheless, the Russians managed to read a significant part of the US Navy Submarine Command KL-7 and KL-47 traffic for nearly 17 years (see below).


Key lists   KAK-x
Below is an example of a key list as it was used with the ADONIS operating procedure [C]. The key – i.e. the machine configuration – was changed every day and consists of a table with one line for each day of the month. The columns show the configuration of rotor position from left to right.


Each column holds the information for one rotor, for example
H 24 8-D
for position 1. In the example, wired rotor (core) 'H' will be used in the first position. It's alphabet ring must be set to 24 (i.e. 'R'). It is fitted with notch ring '8', of which the markings are lined up with the letter 'D'.


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Interior
Base Unit   KLB-7
The KLB-7 — shown in the image above — is the actual chassis on which the machine is built. It accomodates the electronic valve-based circuits and a mechanical gearbox. It is responsible for the synchronisation of the various parts and consists of a motor, a generator, a timing unit, a printer etc. In the image above it is located at the left side of the machine. The keyboard at the front is also part of the base unit. Note that the KLB-7 never was a classified item. Apparently, the electro-mechanical base unit was not considered to reveal any cryptographic secrets.


Stepping unit   KLA-7
The rotors are held in position by a locking lever (1). This is a spring-loaded arm that reaches under the wheel from the rear. At the end of the arm is a small sharp lug, that locks into a narrow rig (gap) between the index letters on the circumference of the rotor. Further towards the front, at the bottom of the drum, is the transport lug (2). These lugs are driven by the main gear and lock into the same gaps on the index ring. They move forward, which means that the front face of a rotor moves upwards when the wheel makes a step, and that the letters pass by the window in ascending order. On each key-press a rotor can only make a single step (or stay in position).

Whether or not a rotor moves when a key is pressed, depends on the presence or absense of a lug on the stepping ring of one of the other rotors. The stepping ring of each rotor is sensed by a switch (3) towards the front of the basket.

Please note that the switches sense the stepping ring 10 positions further on the circumfere of the rotor. In other words: when the rotor is at A (visible in the window at the white line), the lug of position H is sensed. The switch activates a solenoid (L1 thru L7) that allows the rotor to be moved when the gearbox makes a single step.
  
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When setting the daily key, the start position of the rotors can be altered manually by pressing the keys (4). This can only be done when the machine is in plain-text mode. (P). Pressing the key briefly advances the rotor by one position. Holding it down, advances the rotor repeatedly.

Rotor movement control is complex, but is fixed by the internal wiring. Although details about the rotor stepping mechanism were not published until March 2021, it appeared to be possible to deduce the wiring, simply by observing the rotor movements whilst the machine is running. In 2011, Crypto Museum was able to reconstruct the circuit diagram below, based on observations:

KLA-7/TSEC Circuit Diagram

Please note that the sensing switches at the top are in the sequential order (1 to 7), but that the order of the manual stepping switches and the solenoids is mixed. This is done to improved the redability of the circuit diagram. The stepping unit as presented here is implemented identically in Dirk Rijmenants' KL-7 Simulator, and has since been confirmed to be correct by former users. It was also verified against the original circuit diagram when it was released in March 2021 [E][F].

Stepping unit - seen from the front right
Stepping unit - seen from the front left
Stepping unit - front view
Stepping unit - rear view
Stepping unit - bottom side
Stepping unit
Close-up of the stepping levers of the stepping unit
Stepping the rotors
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Stepping unit - seen from the front right
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Stepping unit - seen from the front left
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Stepping unit - front view
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Stepping unit - rear view
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Stepping unit - bottom side
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Stepping unit
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Close-up of the stepping levers of the stepping unit
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Stepping the rotors

Keyboard
The keyboard of the KL-7 is part of the KLB-7 base unit. It consists of 29 green keys and a black space bar. It has the standard QWERTY layout divided over three rows. The numbers (0-9) are shared with the top row. At the bottom right are three special keys marked LET, FIG and RPT.

Each key is in fact an electric switch, consisting of a contact and a spring, mounted below the key cap. When a key is pressed, the contact is grounded (i.e. connected to the 0V rail), which allows the pulse-generator to issue a pulse. The keyboard interior is visible in the images below.

When entering numbers, the user must first press the FIG-key (figures). This acts like the shift-key on a modern computer. As long as the machine is in numbers-shift mode, a large neon lamp behind the keyboard is lit. When reverting to letters, the LET-key has to be pressed first.
  
Operating the keyboard of the KL-7

Some KL-7 machines have been upgraded with the KLX-7 input/output interface. This option consist of two parts: a contact unit that is mounted between the keyboard and the base, and the actual KLX-7 interface that is mounted behind the rotor basket. When the KLX-7 is fitted, the keyboard is removed and the contact unit is mounted in its place. The keyboard is then refitted on top of the contact unit. As a result, the keyboard will be positioned slightly higher than before.

Mode selector
An encrypted KL-7 message consists only of the 26 letters of the Latin alphabet. In order to allow the source text to contain letters, numbers and spaces, special tricks are used. This is done by surendering a couple of letters and using them for SPACE, Letter-shift (LET) and Figures-shift (FIG). The surendered letters are then no longer available and must be replaced by another one.

Furthermore, the operation has to be reversed when switching from encryption to decryption. This is achieved by the MODE-selector, which is hidden under the keyboard. This MODE-selector consists of a large pertinax board with contacts at either side, much like a PCB (but thicker).

It is operated by the rotary knob to the left of the keyboard. The image on the right shows the MODE-selector being operated. It has 4 settings: Off (O), plaintext (P), encrypt (E) and decrypt (D). In the image, it is in the encrypt (E) position. The MODE-selector also acts as the power switch (O).
  
Operating the MODE-switch

The MODE-selector is basically a large slide-switch with multiple contacts. When operating the knob, the large brown pertinax board moves from right to left. It has four possible positions, each of which corresponds with one of the settings of the MODE-selector. When pressing a key, a spring-loaded contact is pushed down onto one of the oval contact on the top side of the board.

Cross-section of the KL-7 keyboard, permutor and base unit

The oval contacts at the top side are connected to a different set of contacts at the bottom. The contacts at the bottom, are sensed by a set of fixed spring-loaded contacts in the base unit. The diagram above shows a simplified cross-section of the keyboard, the sliding pertinax board – known as the permutor – and the fixed panel with spring-loaded contacts at the bottom (base).

KL-7 in plaintext mode (P)

The diagram above shows what happens when a key is pressed whilst the machine is in plaintext mode (P). The contact of the W-key touches the top pf the T-shaped contact of the permutor, and is sensed by a spring-loaded contact in the base unit, which passes it directly to the printer.

KL-7 in decryption mode (D). Move the mouse out of the drawing to see the current flow in encryption mode (E)
Move the mouse over the diagram to see when happens in decryption mode

When the machine is a encryption mode (E), the permutor is moved one position to the left and the contact of the W-key is connected to the input of the rotor drum. In the example, the wiring of the rotor drum converts the letter 'W' into the letter 'E', which is then sent to the printer.

Move the mouse over the image to see what happens when the letter 'E' is pressed whilst the machine is in decryption mode (D). The complex double-side permutor basically reverses the input and output contacts of the rotor drum, and ensures that the machine is reciprocal.

Key mapping
The machine can handle 37 characters: the 26 letters of the Latin alphabet (A-Z), the 10 digits (0-9) and SPACE. The ciphertext however, consists only of the 26 letters of the alphabet (A-Z). This is achieved by switching between letters (LET) and numbers (FIG) – similar to a teleprinter – at the expense of three letters: J (FIG), V (LET) and Z (SPACE). When encrypting, both the letters 'J' and 'Y' will be mapped onto 'Y', whilst 'Z' and 'X' are both mapped to 'X'. This means that the decrypted text will look slightly different from the original plaintext, but will still be readable.

    THE 236TH QUICK RED FOX JUMPED 780 TIMES OVER THE 1459 LAZY BROWN DOGS
    THE 236 TH QUICK RED FOX YUMPED 780 TIMES  OVER THE 1459  LAXY BROWN DOGS
    
The first line shows the entered plaintext¸ whilst the second line shows the text after it has been encrypted and decrypted. Note the extra spaces that are inserted when switching back from FIG-mode to LET-mode. Also note that the letter 'J' has been replaced by 'Y' and that 'Z' has become 'X'. The letter 'V' (used for switching to LET-mode) is not replaced by another letter. In FIG-mode its function is to return to LET-mode (and insert a space), and in LET-mode it simply acts as a 'V'.

Plaintext J V X Y Z FIG LET SPACE
Encryption Y V X Y X J V Z
Decryption Y LET/V X Y X FIG LET/V SPACE
MODE-selector
Inside the top lid
Operating the MODE-switch
Keyboard and MODE-selector
Keyboard
KL-7 with keyboard removed
Inside the keyboard
Sliding contact panel below the keyboard
Sliding contact panel - top side
Sliding contact panel - top side
Sliding contact panel - bottom side
Sliding contact panel - bottom side
Silver-plated contacts on the sliding contact panel
MODE-selector detail: 5-letter spacing actuator
Close-up of the numbers-shift lamp (FIG)
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MODE-selector
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Inside the top lid
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Operating the MODE-switch
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Keyboard and MODE-selector
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Keyboard
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KL-7 with keyboard removed
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Inside the keyboard
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Sliding contact panel below the keyboard
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Sliding contact panel - top side
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Sliding contact panel - top side
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Sliding contact panel - bottom side
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Sliding contact panel - bottom side
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Silver-plated contacts on the sliding contact panel
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MODE-selector detail: 5-letter spacing actuator
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Close-up of the numbers-shift lamp (FIG)

Gear box
At the heart of the KL-7 is a very compact, yet complex, mechanical unit. It consists of a DC motor, and AC high-voltage generator, a printer, a pulse generator and a timing unit. All components are driven by the DC motor, either directly, or through a 3:1 cog-wheel reduction.


The motor and the generator are mounted on the same axle, and rotate at 6600 RPM (revolutions per minute). Through a 3:1 reduction unit, the pulse generator and printer are driven at a spreed of 2200 RPM. This speed is further reduced to drive the complex timing unit. This timing unit – mounted below the other parts – is repsonsible for the single step operations (shown in purple).

Unlike the other parts of the gearbox, the timing unit does not rotate continuously. Instead, a cluch – driven by the electronic circuits – is used to couple it to the main axle, after which it will complete a single revolution during which a set of 4 cam-controlled switches provide the timing signals for the electronics. The timing unit also drives the KLA-7 stepping unit (and hence the rotors), and the paper feed. On each revolution, the rotors can be advanced by one position.

The complex gearbox is located in the left half of the KL-7, and is a fixed part of the KLB-7 base unit, as shown in the image on the right. The motor is at the rear of the unit (at the right in the image). Imediately in front of the motor (the part with the two recessed screws) is the high-voltage AC generator, or invertor. It produces the anode voltage for the valves.

In front of the inverter is the pulse generator, which is further described below. At the bottom – below the other parts – is the timing unit which is responsible for the overall system timing.
  
Printer and timing unit

The printer is located at the front of the gearbox assembly. This part is visible at the left in the above image, and can be recognised by the black cap that covers the ink ribbon. The printer is fed by a paper strip from the paper supply reel that is mounted to the right side of the gearbox. The paper leaves the printer at the left. The print head rotates continuously, whilst the print hammer and the paper transport are operated by the single step mechanism of the timing unit.

Printer and timing unit
Gear-box
Model plate of the gear-box, entitled 'Inverter'
Left view of the KL-7, giving a good view of the Inverter, just behind the bracket
Gearbox and timing unit - seen from the rear of the machine
Timing unit
Timing unit
Timing unit
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Printer and timing unit
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Gear-box
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Model plate of the gear-box, entitled 'Inverter'
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Left view of the KL-7, giving a good view of the Inverter, just behind the bracket
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Gearbox and timing unit - seen from the rear of the machine
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Timing unit
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Timing unit
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Timing unit

Pulse generator
The timing for the printer comes from a pulse generator that is coupled to the axle of the gear box. This axle also drives the printer and the timing unit at 2200 rpm. The pulse generator consists of 37 coils in a circular arrangement, with a rotating armature at the centre. Of these coils, 26 are used for the letters of the alphabet, 10 for the numbers (0-9) and one for SPACE.

The image on the right shows the front side of the bare pulse generator. The coils are divided over two rings: one at the front with 19 coils, and one at the rear with 18 coils (plus a dummy).

The rotating armature has two slightly displaced magnets; one for each circle of coils. Each of the coils is connected in series with one of the keys of the keyboard. When the user presses a key, the corresponding coil is connected to ground and produces a small electric pulse as soon as the magnet on the rotating armature passes by. The remaining coils do not produce a pulse.
  
Pulse generator - front

The pulse from the active coil is conditioned – using a step-up transformer and a pulse sharpener – and passed to the printer. The keys on the upper row of the keyboard activate two series-connected coils: one for a letter and one for the corresponding digit. As a result, they will produce a double pulse, of which the second one is stronger and slightly delayed (due to the displaced magnet on the armature). In FIG-shift mode, a gate circuit selects the second one.

Pulse generator - front
Pulse generator - rear
Coils inside the pulse generator
Pulse generator contact block
Pulse generator armature. Note the two displaced magnets.
Pulse generator armature
Pulse generator armature
 Pulse generator armature
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Pulse generator - front
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Pulse generator - rear
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Coils inside the pulse generator
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Pulse generator contact block
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Pulse generator armature. Note the two displaced magnets.
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Pulse generator armature
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Pulse generator armature
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 Pulse generator armature

Printer
The KL-7 has a built-in printer with a continuously rotating print head, that prints its output onto a narrow 9.5mm (3/8") pre-gummed paper strip, similar to the American M-209 and the Russian Fialka. It is located at left – just behind the keyboard – and is the frontmost item of the gearbox.

The printer has an oval-shaped black cap, that covers the ink ribbon spools. The image on the right shows the printer after this cap has been removed. At the top are ink ribbon supply and pickup spools. Below the spools is the circular print head. Paper is supplied by a circular metal cage that is located to the right of the gearbox.

The print head contains 37 symbols (A-Z, 0-9 and space) and runs continuously. When a letter is to be printed, a hammer is released when that letter is opposite the paper strip, under control of the pulse generator and the electronic circuit.
  
Printer

After each printed symbol, both the paper strip and the ink ribbon are advanced by one position. The design of the printer is nearly identical to that of the SIGABA; the wartime predecessor of the KL-7. The ink ribbon spools are smaller than usual, but a spare one is stowed inside the case lid.

Printer and timing unit
Printer
Printer - front view
Printer seen from the front
Paper path
Removing the cap from the printer
Paper transport
Close-up of the print hammer solenoid
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Printer and timing unit
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Printer
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Printer - front view
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Printer seen from the front
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Paper path
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Removing the cap from the printer
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Paper transport
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Close-up of the print hammer solenoid

Optional enhancements
Tandem unit   EZ-KL7
In operation, the KL-7 was not one of the most reliable machines. It fact, it was known for its many contact problems, some of which were, no doubt, related to bad or improper maintenance. Many former users recall their struggles with the KL-7 in order to properly process a message.

The German Army (Bundeswehr) even developed an assembly known as the EZ-KL7, that allowed two machines to run in tandem (i.e. in parallel) so that errors could be detected. The EZ-KL7 unit was mounted in front of the keyboard of one of the two KL-7 machines and continuously compared their outputs. As soon as a difference was detected, an alarm was raised. Note that EZ-KL7 is pronounced 'Easy KL-7'. Image via [13].

This option required the KLX-7 input/output interface to be installed (see below).

  
KL-7 with KLX-7 and EZ-KL7 attachment [13]

Teleprinter interface   KLX-7
On its own, the KL-7 only accepts input from the built-in keyboard, whilst the output is available only as printed text on a narrow paper strip. In order to connect the KL-7 directly to teleprinter equipment, the KLX-7 input/output interface was available as an option. As far as we currently know, the KLX-7 consisted of two parts, one of which was mounted between the keyboard and the base. This required the keyboard to be removed, after which a contact unit was mounted in its place. The keyboard was then refitted on top of the contact unit. The actual input/output interface itself, was mounted at the rear of the machine, behind the rotor basket (see above).


In order to read input directly from a 5-level teleprinter tape, the optional HL-1 tape reader was connected to the input of the KLX-7, as show in the diagram above. The KLX-7 interface was also needed if the German EZ-KL7 tandem option was installed, most likely in this manner:



Compromise
During its lifetime, KL-7 was compromised on a number of occasions. It is believed that the Russians were able to read (break) messages encrypted with a number of high-level US cipher machines, including the KW-7, the KL-7 and the KL-47. The latter is a variant of the KL-7, used by the US Navy's Command Center for Atlantic submarine forces [5]. It is slightly bigger than the KL-7 and features a paper tape reader, a tape puncher and a different (teletype) keyboard.

Walker spy ring
Arguably the most 'famous' story of cipher compromise is that of John Anthony Walker, born 1937, who worked for the US Navy and successfully spied for the Russians for nearly 17 years [4].

Walker joined the US Navy in 1955 and started spying for the Soviets in December 1967, when he had financial difficulties [6]. From that moment, until his retirement from the navy in 1983, he supplied the Russians with the key lists and other critical cipher material of the KL-47, the KW-7 and other cipher machines.

For his information he received several thousand dollars from the Soviets each month. In 1969 he began searching for assistance and befriended Jerry Whitworth, a student who would become a Navy Senior Petty Officer. In 1973, he was able to enlist Whitworth in his spy-ring.

In 1976, Walker left the Navy to become a Private Investigator (PI) but kept spying for the Russians. By 1984, he had enlisted his older brother Arthur and his son Michael, who kept the endless flow of classified documents going for another year. He also tried to recruit his youngest daughter who had just started to work for the US Army, but this attempt failed when she became pregnant and abandoned her military career.
  

Earlier, around 1976, Walker and his wife Barbara divorced after a history of physical and alcohol abuse [6]. When Walker refused to pay alimony in 1985, she tipped-off the FBI, which eventually led to his arrest. After his arrest, Walker cooperated with the authorities and made a plea bargain in order to lower the sentence of his son Michael. Suffering from Diabetes and throat cancer, John Walker died in prison on 28 August 2014. His son was released on parole in February 2000.

Lost in Vietnam
Another example of compromised KL-7 security, is the loss of approx. 700 ADONIS (KL-7) and NESTOR (KY-8) devices in Vietnam in February 1975 [14]. Earlier in the Vietnam War (~1970), the Americans had decided to provide the Republic of Vietnam (RVN) with limited quantities of cryptographic equipment, such as the M-209 and KL-7 cipher machines, various One-Time Pad (OTP) systems, voice authentication codes and some NESTOR (KY-8) voice encryption units.

After the withdrawal of American troops from Vietnam, the cryptographic depot, known as Don Vi' 600, stayed in place, with American personnel accounting for the crypographic items. In late 1974 and early 1975, the situation worsened and the Americans began to withdraw some of the equipment, with the intent of sending it back to CONUS 1 or Hawaii.

When in January/Februari the situation became critical, priority was given to removal of the equipment to Don Vi' 600 so that it could be moved to CONUS immediately. In the last three weeks of the existence of the RVN, some 700 pieces of ADONIS and NESTOR equipment had been gathered and prepared for shipment to CONUS, but none of this equipment was shipped or destroyed in time. Eventually the equipment fell into North Vietnamese hands.

Whilst the M-209 was considered obsolete by the Americans, the KL-7 and the NESTOR equipment certainly was not. It is quite likely that the North Vietnamese eventually sold some of the machines to the Russians and possibly also to the Chinese, along with 12 months worth of key material and one-time pads that were also found in Don Vi' 600.

  1. CONUS = Continental US.

Rotor reader
The information passed by John Walker and his spy ring, allowed the Russians to build an analog of the KL-7 and to find ways to mount a cryptanalytical attack on the machine [5]. This allowed the Russians to decrypt at least one million sensitive classified (TOP SECRET) messages [7].

The Russians even supplied Walker with a small device, known as a rotor reader, that allowed him to trace the internal wiring of each rotor [2].

The image on the right shows the device, as it was confiscated by the FBI. It was small enough to be carried inconspiciously, and could easily be hidden in a pocket. When folded it measures approx. 7.5 x 10 cm (about a pack of cigarettes).

The device consists of two halves that are kept together by springs and hinges. Once opened, 36 flat-faced contacts become visible. They mate with the 36 spring-loaded contacts of a KL-7 rotor (photograph supplied by Keith Melton) [2].
  
Photograph published here with kind permission from the author.

A hand-operated slide contact, stowed inside a storage compartment at the top left, was then inserted through the center hole of the rotor. It kept the rotor in place, provided the correct pressure for the spring-loaded contacts, and allowed the slide contact to 'brush' over each individual rotor contact at the other side. The rotor would be placed with index arrow opposite the position 0 index of the reader. The slide contact was then moved over the individual contacts of the rotor, and each time one of 36 lamps on the lamp panel (at the left) would be lit.

Below is a 3-D drawing of the rotor reader. It gives a good idea of how it was used. The manually operated slide contact is here taken out of its storage compartment. It has a rectangular 'key' at the bottom (left in the drawing) that is inserted in the rectangluar hole at the center of the reader.

3D view of the rotor reader. Copyright Paul Reuvers 2011.

It is assumed that the rotor reader was not one-of-a-kind, but that at least a modest quantity of them was built. The Soviets supplied Walker with the device only three weeks after he started spying for them in 1967. Furthermore, Walker was not the only person who compromised the KL-7 and similar machines. When Army Sergeant Joseph Helmich was caught spying in the mid-1970s, an identical rotor reader was found on him [5].


KL-7 Simulators
Windows   Dirk Rijmenants
In 2009, Dirk Rijmenants managed to crack part of the KL-7 mystery. From information received from researchers and former KL-7 users all over the world, combined with his own observations, he managed to put together an attractive KL-7 Simulator for Windows™ [18]. Since then, he received numerous e-mails with new information about the working principle of the machine.

Version 5.0.1 - 27 May 2013

In February 2011, after we uncovered the secrets of the stepping unit of the KL-7 (KLA-7/TSEC), Dirk released a major update of his simulator, which includes the new stepping unit plus a number of corrections to the operation of the mode-selector below the keyboard. It now also includes realistic sounds, sampled from a real KL-7 in operation. This simulator has been verified against real KL-7 machines.

The image on the right shows a screenshot of the KL-7 Simulator running on Windows XP.

 Download KL-7 for Windows (off-site)
  
Click here to download the KL-7 Simulator for Windows

Java   MIT
In September 2012, we teamed up with some researchers of the Cyber Systems and Technology Department of the Lincoln Laboratory of the Massachusetts Institute of Technology (MIT) in Lexington (MA, USA), to produce a Java version of Dirk Rijmenants' KL-7 Simulator for Windows (see above). The main advantage of using Java over Windows, is that the application can run on any platform that supports the Java language, including Windows, Mac (Apple), Unix and Linux.

Version 5.0.2 - 22 December 2013

In February 2013, Uri Blumenthal of MIT, released the first version of the JAVA KL-7 Simulator. As it uses the graphics from Dirk Rijmenants' KL-7 Simulator for Windows (above) and the sounds and other information – provided by Crypto Museum – the two simulators have a very similar appearance.

The software comes as a JAR archive and works 'out of the box' on most platforms, including the Apple Macintosh. An extensive 30-page manual is included with the software. Simply click the question mark (?) at the top bar to read it. It even has a built-in codebook generator.

 Download JAVA KL-7 Simulator
  
Click here to download the Java KL-7 Simulator

Please note that the above KL-7 simulator requires the latest version of JAVA (8) to be installed on your computer. For security reasons it is always recommended to use the latest version of JAVA. To check your current version and download the latest version of JAVA, click here. If you are still using JAVA version 6 or 7 and do not want to upgrade yet, you may download the JAVA-6 or 7 compatible version of the KL-7 simulator below. There is no support for these versions.

 Download JAVA-7 compatible version of KL-7 Simulator
 Download JAVA-6 compatible version of KL-7 Simulator


Audio sample
The audio file below illustrates the use of the KL-7. First, the machine is turned on. Then 10 keys are typed in plain text mode. The unit is then switched to encryption, after which 7 letters and 5 spaces are typed. It is then switched to decryption, after which 8 letters are typed. We then switch to encryption and then to plain text. Next, the rotor positions are changed. Finally, the KL-7 is switched off again and you can hear the motor fading out.

Connections
Power
The KL-7 must be powered by a 24V DC source, that should be connected to the short piece of cable to the right of the keyboard. It has a 2-pin Amphenol 97-series (male) plug at the end, that mates with the 2-pin (female) socket on the power cable (stowed in the case lid) and on the external PSU. The required (female) socket has the following part number: Amphenol 97-series MS3101A12S-3S (shell: AN3057-4). Below is the pinout of the (female) socket on the PSU:

  1. +24V
  2. 0V
Known locations
  1. This unit is known to have been de-militarised.
  2. Formerly: Maritime Command Museum

Related patents
Specifications
  • Name
    KL-7
  • Designator
    AFSAM-7, TSEC/KL-7
  • Developer
    NSA
  • User(s)
    US Navy, US Army, NATO, FO
  • Introduced
    1952
  • Last used
    1983
  • Declassified
    2009, 2021
  • Rotors
    8
  • Contacts
    36
  • Power
    24V DC
  • Weight
    9.3 kg
Nomenclature
Part Old name New name Description
KL-7 AFSAM 7 TSEC/KL-7 Complete machine
KLB-7 AFSAM 7/1 KLB-7/TSEC Base unit
KLA-7 AFSAM 7/2 KLA-7/TSEC Stepping unit
KLK-7 AFSAM 7/3 KLK-7/TSEC Rotor basket (drum)
KAR-x ? ? Rotor set
KAK-x ? ? Key lists
KAM-1 ? KAM-1/TSEC Maintenance manual [E]
AFSAG 1236 AFSAG 1236 ? Interim operating instructions [D]
KAO-41C ? KAO-41C/TSEC Operating instructions [C]
KAO-83 ? KAO-83/TSEC Operator's manual (wanted)
Documentation
  1. KAO-83/TSEC — wanted
    Official operator's manual for the KL-7.

  2. NSA, TSEC/KL-7 Canadian User Report After First Year of Operation
    National Security Agency. CSEC 115. 1 May 1959, 15 pages. SECRET. 1

  3. NSA, Operating Instructions for TSEC/KL-7 ADONIS Operation
    Department of Defense. National Security Agency. Washington, DC 20305.
    KAO-41C/TSEC. September 1966, 28 pages, Confidential - Crypto. 1

  4. NSA, Interim Operating Instructions for Pollux Cryptosystems-Joint
    Department of Defense. Armed Forces Security Agency. Washington 25, DC.
    AFSAG 1236. January 1953, 45 pages, Confidential Security Information. 1

  5. NSA, Repair and Maintencance Instructions for TSEC/KL-7
    AFSAM-7. KAM-1/TSEC, 1 May 1955. Last updated 3 February 1960. 2

  6. NATO, TSEC/KL7 Circuit Diagram
    AMSP-519/A. NATO RESTRICTED. 3
  1. NSA information declassified and approved for release on 21 April 2011. FIOA Case # 64246. CSEC information declassified and approved for release on 28 April 2011. CSEC ATIP Case # A-2010-00015.
  2. Document declassified by NSA on 30 March 2009 (E.O. 12958, FOIA 47709). Obtained via Bill Neill and scanned by Nick England in March 2021 [16]. Reproduced here by kind permission.
  3. Anonymous donor, March 2021.

References
  1. H. Keith Melton, Ultimate Spy
    1996-2002. ISBN: 0-7513-4791-4. p. 54.

  2. H. Keith Melton, The Ultimate Spy Book
    2009. ISBN: 07894074435.

  3. NSA, Cryptologic Almanac 50th Anniversary Series, AFSAM-7
    Retrieved November 2010. Via WayBack Machine (April 2021).

  4. TruTV, Family of Spies: The John Walker Jr. Spy Case
    Retrieved November 2010.

  5. Laura H. Heath, Analysis of Systematic Security Weaknesses of the US Navy...
    M.S., Georgia Institute of Technology, 2001. Fort Leavensworth, Kansas (USA), 2005. Thesis of Major Laura Heath, detailing how John Walker exploited weaknesses in the US Navy Broadcasting System between 1967 and 1974.

  6. Wikipedia, John Anthony Walker
    Retrieved November 2010.

  7. FBI, The Year of the Spy
    Famous Cases and Criminals. John Anthony Walter Jr.
    Retrieved November 2010.

  8. NSA, TSEC/KL-7 Canadian User Report After First Year of Operation
    National Security Agency. CSEC 115. 1 May 1959, 15 pages. SECRET. 1

  9. NSA, Operating Instructions for TSEC/KL-7 ADONIS Operation
    Department of Defense. National Security Agency. Washington, DC 20305.
    KAO-41C/TSEC. September 1966, 28 pages, Confidential - Crypto. 1

  10. NSA, Interim Operating Instructions for Pollux Cryptosystems-Joint
    Department of Defense. Armed Forces Security Agency. Washington 25, DC.
    AFSAG 1236. January 1953, 45 pages, Confidential Security Information. 1

  11. Chuck Aston, Former KL-7 maintenance engineer at USAF
    Personal correspondence, Febrary 2015.

  12. CSP-6620A, TSEC/HL-1 and TSEC/HL-1B system block diagrams
    4 June 1962. Unclassified.

  13. Klaus Schmeh, Die Welt der geheimen Zeichen
    2004. ISBN 3-937137-90-4.

  14. Joachim Beckh, Blitz und Anker - Band II
    2005. ISBN 3-8334-2997-6. p. 282.

  15. James Bamford, Body of Secrets
    2008. ISBN 1407009206. pp. 352-353.

  16. Nick England, US Navy Crypto Equipment - 1950's-60's
    May 2016 — March 2021.

  17. Crypto Museum, The Gentleman's Agreement
    30 July 2015.

  18. Dirk Rijmenants, TSEC/KL-7 ADONIS & POLLUX
    Cipher Machines & Cryptology, 2004-2021.
  1. NSA information declassified and approved for release on 21 April 2011. FIOA Case # 64246. CSEC information declassified and approved for release on 28 April 2011. CSEC ATIP Case # A-2010-00015.

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