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Noreen   BID/590
One-time tape cipher machine

Noreen was a small portable off-line one-time tape (OTT) cipher machine, developed in the UK in the early 1960's and used for diplomatic traffic by the British Commonwealth 1 as a replacement for (or complementary to) the Rockex cipher machine from WWII, with which it was compatible. The machine is also known as BID/590 (with variants like the BID/590/2) 2 and as Mk-854M.

Noreen is suitable for use in teleprinter networks that use the digital 5-bit ITA-2 code, also known as Murray Code or Baudot. It uses the principle of the one-time pad by mixing each plain­text character with a random character from a key­stream tape, using the mathematical modulo-2 or XOR operation. This operation is known as the Vernam Cipher and is commonly used by other mixers such as the ETCRRM, and the Ecolex 4.

Without the external tape feeder, the machine measures just 33 x 27.5 x 17 cm, making it one of the smallest machines in the mixer class.
Noreen with keytape

Noreen is compatible with Rockex, a WWII valve-based online/offline cipher machine that was introduced in 1943. It uses the same 6-level keystream tapes, but contrary to Rockex, Noreen can not produce its output directly on punched paper. Instead, the encrypted (or decrypted) text is printed onto a pre-gummed 9.4 mm paper strip by a rotary printer at the front of the unit. The paper strips were then glued onto blank sheets of paper and re-typed on a common teleprinter.

Example of a ciphertext produced on Noreen

Noreen was introduced in the early 1960's in the UK, where it was was used by the Foreign and Commonwealth Office (FCO). By special arrangement, the technology was shared with Canada, where it was used by the Office of External Affairs (now: Foreign Affairs). The machine was also used by Australia and New Zealand, but only for confidential communication with the UK [3].

The machine was initally marked as secret and confidential. Althoug this is generally the case with cryptographic equipment, mixing machines were commonly unclassified devices as they do not contain any secret circuitry. With most other mixers, it was the combination of the machine and a secret classified keystream tape that had to be treated as confidential. Noreen entered service in 1962/63 and was used until the early 1980's. The machine has since been declassified.

  1. In this context, the expression 'British Commonwealth' is used to identify the following countries of the Commonwealth of Nations: Great Britain, Canada, Australia and New Zealand.
  2. BID means British Inter Departmental. Systems with a BID designator are generally used by more than one single governmental agency or department. More...

Noreen with keytape Noreen without cover and paper strip Front view Rear view Top view Key tape moving through the 6-channel tape reader Mode selector and LETTER LOCK button Microswitch mounted under the Carriage Return (CR) key

Noreen roughly consists of three sections: the keyboard at the front, a mechanical section at the rear (mounted on a die-cast chassis) and the transistor-based electronic circuits at the bottom. The diagram below shows the machine after the dust cover has been removed. The circular black paper tray has been made partly transparent here, so that you can see what is behind it.

The machine is switched ON by connecting a suitable battery pack or PSU and placing the MODE selector at the front right in the EN position for encoding or to DE for decoding. It can also be used for typing and printing plaintext, by placing the MODE selector in the OFF position.

An external paper tape feeder is normally attached to the right side. It supplies the keystream tape to the 6-channel tape reader at the left rear. When starting a (de)coding session, the tape should be placed at the first character of the cipher block (i.e. the first character of the message indicator on the keystream tape. The operator then enters the first character of the message.

Noreen has only two physical connections which are both located at the rear. A fixed multi-wire black cable with a 10-pin connector at the end is used to connect the machine to a special TEMPEST approved battery unit. Furthermore, a 3-pin Bulgin socket is present for connection of the tape sensing switch on the external paper tape feeder (not shown here). This sensing switch was used to detect whether a keystream tape for encoding or decoding was present in the feeder.

Front view (with paper strip) 1/2 Front view (without paper strip) 2/2 Rear view Rear view Indicators and switch Mode selector and LETTER LOCK button Key tape supply reel connection Key tape ready for use
  • BID/590
    Initial version of Noreen. Introduced around 1962. Modified several times during its lifetime, for example with TEMPEST improvements.

  • BID/590/1
    Differences with BID/590 currently unknown.

  • BID/590/2
    Improved version with character counter mounted under the keyboard. Introduced around 1969. Modified 11 times during its lifetime. This is the machine featured on this page.

  • BID/591
    Noreen instruction manual.
Keystream tape
Noreen has a built-in tape reader at the top left. This tape reader is used for the so-called key­stream tape : a punched paper tape that is filled with random characters A-Z. As the international teleprinter alphabet (ITA2) is based on 5-bit data, one would expect a 5-level tape reader in this position, but this is not the case. Noreen's keytape reader expects a 7/8" wide paper tape, with 6-bit data. This means that a rather uncommon format was used for the keystream tape.

Noreen key tape compared to 5-level teleprinter tape

In the image above, the two tape formats are compared. At the right is a common 5-level teleprinter tape (blue). The one on the left is the Rockex/Noreen key tape (red) which has an unusual width and was probably custom made. It is seen from the front/top of the machine. Note that the extra tape channel (6) was added before channel 1 and that a margin was added at the side of channel 5, probably to prevent the tape from being inserted the wrong way around.

The keystream tape contains a random character data stream in the usual 5-level teleprinter format. This 5-bit information is mixed with the data from the keyboard. Whenever a hole is present in channel 6 however, the data is not enciphered but is sent directly to the printer. This way a space can be inserted in the printed text after each 5th character, while a double space was inserted after each 5th group. Channel 6 was also used to automatically insert the (unencrypted) 5-letter message indicator that marked the beginning of each section of 49 five-letter groups.

The keystream tapes were compatible with those of the Rockex cipher machine, and were created by means of a so-called paragrapher device. This device punched random A-Z letters on the paper tape in blocks of 50 groups of 5 letters each. The first 5-letter group was the actual message indicator which was not encrypted. This was done by punching the 6th hole in the key tape. The indicator group was followed by 49 encoded 5-letter groups. Each group was separated by a single space (again, using the 6th hole) with a double space after each 5th group [1].

Example of a Noreen key tape

The image above shows an example of a keytape as it is guided through the tape reader. This means that channel 5 of the tape is at the bottom (at the edge with the wide margin) and that the extra channel (6) is added before channel 1 and is now at the top. Note that the random data on the key tape consists only of the letters A-Z. This was done to ensure, in combination with the so-called discriminator, that only the letters A-Z would appear in the encrypted output, e.g.:

Example of a ciphertext produced on Noreen

The ciphertext was printed by the built-in printer onto a pre-gummed paper strip. Once the message was complete, the long paper strip was cut into pieces of equal length and glued onto a blank message form, so that it could be sent by morse code or retyped on a teleprinter, e.g.:

Example of a Noreen ciphertext message sheet

Separate tapes were used for encoding and for decoding. They were idendified by their colour and by the colour of their core. In the UK, the encoding tape was generally green and was wound on a blue marked core. The decoding tape was red and was wound on an orange marked core. In Canada the tapes were coloured yellow and red respectively. The core for decoding was slightly wider than the one that was used for encoding. A sensing switch in the keytape supply reel (connected to the 3-pin socket at the rear), informs Noreen of which tape is used. Using a decode tape in encoding mode does not work. This was done to avoid double use of a keystream tape.

Key tape in secured can 6-channel tape reader Key tape ready for use Key tape entered into the 6-channel tape reader Key tape moving through the 6-channel tape reader Key tape moving through the 6-channel tape reader Tape reader seen from the rear Tape reader
Noreen (BID/590) was developed in the late 1950s and early 1960s, probably as a lightweight replacement for the rather bulky and heavy valve-based Rockex one-time tape cipher machine that had entered service in 1943. It was developed by the Special Communications Unit of the Secret Intelligence Service (SIS, now MI6) at Borehamwood 1 (UK), where also the secret key tapes were produced [2]. In the UK, operators were given a two week course at the Foreign Office at King Charles Street in London, where they were trained in its operation and maintenance. Another training school was at Fort Monkton in Portsmouth Harbour [3]. In the late 1960s or early 1970s, the production of Noreen was moved to HMGCC at Hanslope Park (UK).

Being a one-time tape device, or mixer, Noreen was used exclusively for messages at the highest level of secrecy. Whilst intended for confidential diplomatic traffic of the UK only, the technology was shared with Canada, with whom the UK historically had a special relationship. Furthermore, machines were installed in Austrialia and New Zealand, but only for confidential traffic with the UK. In Australia, they were installed in Darwin, Canberra and Wellington. Whilst Canada produced its own key-tapes, the tapes for the UK, Australia and New Zealand were all prepared in the UK.

During its lifetime, operators and service personnel were not allowed to take the circuit diagrams or any other documentation out of the building. They were classified as secret and confidential. The only piece of documentation that came with each Noreen, was the destruction protocol that had to be followed in case of an emergency or compromise. Any surviving documentation about Noreen (which is now unclassified) would be greatly appreciated.

  1. Noreen was developed at HMGCC, Her Majesty's Government Communications Centre, at Boreham Wood, before the technical development centre was moved to Hanslope Park in 1970. More...

Block diagram
The drawings below illustrate the operating principle of the Noreen. Central to the system is a set of five XOR circuits that 'mix' the input from the keyboard with the keystream tape. Each time a character is typed on the keyboard, a random character is read from the keystream tape. Both characters are then 'mixed' by the XOR circuit and are then printed on a pre-gummed paper strip. This operation is generally known as the Vernam Cipher and such machines are called 'mixers'.

Principle of the Vernam Cipher

The data from the keyboard and the keystream tape, each consists of 5 data-bits. Whenever the 6th hole in the key tape is present however, the data from the tape reader is printed directly, thereby effectively bypassing the XOR circuit. This was used for automatically adding spaces and formatting characters. Conversion of the 32 keys into 5-bit digital codes is done by means of a mechanical encoder, whilst the 5-bit data for the printer is converted into 32 electrical lines by means of a diode matrix. 3 The 32 lines are connected to a commutator at the back of the printer.

Block diagram of Noreen in encipher mode

The keytape only contains the (random) letters A-Z, plus formatting data. In order to ensure that the (printed) output also consists of only letters (A-Z) and formatting data (SPACE, LF, CR), a discriminator is added to check the output of the XOR for unwanted characters (the so-called stunt 1 characters). If, during encoding, a stunt character is encountered, the input is halted and the key character is output instead. Next, the key tape is advanced and the next key character is tried, and so on, until the desired output (A-Z) is yielded 2 . This is then sent to the printer.

Block diagram of Noreen in decipher mode

At the receiving end, the bypassed character is mixed with the same character from the key tape, which produces a NULL code. As a NULL code has no effect in the 5-bit ITA2 code, it will be ignored and has no effect on the decoded text or the security of the cipher. Although some overhead is generated, it has the advantage that all ITA2 characters may occur in the original plaintext, regardless of the A-Z limitation of the ciphertext. The result could be something like:

Example of a deciphered text printed on Noreen

When deciphering as described above, the formatting data from the key tape has to be ignored and any characters entered on the keyboard other than the letters A-Z, will also have to be suppressed. For this reason, a mode selector (EN/DE) is available to the right of the keyboard. In deciphering mode (DE), the machine works as shown in the block diagram above.

 More about the Vernam Cipher

  1. In telegraph speak, 'stunt characters' is a common expression for the control codes: LF, CR, LTRS, FIGS and SPACE.
  2. In May 2015, the exact operation of the Rockex/Noreen key tape has been the subject of a discussion on the Crypto Collectors News Group, in which the method described here was proposed by Frode Weierud [7]. This has since been confirmed by released NSA documents on Rockex [8] and by trying it out.
  3. As it is not possible to use a diode matrix for a 5-to-32 conversion, the actual circuit works the other way around: as a 32-to-5 encoder. Please refer to the description of the printer for further information.

Noreen is built on a die-cast aluminium chassis on which various sub-assemblies are mounted. At the front is a mechanical teleprinter keyboard, which is nearly identical to the keyboard of the American Teletype Model 15 teleprinter. At the top left is a 6-level tape reader that was probably manufactured by Creed. At the centre is a paper strip printer with a two-level rotating print head.

Mounted on top of the chassis are a 6-channel Creed punched-paper tape reader at the left rear, a printer with a rotating print head at the front centre, and a mechanical 5-bit keyboard encoder at the right. The latter is combined with the driving gear and clutch that is driven by a diagonally mounted electromotor at the rear centre. Also mounted on top of the chassis are various solenoids and telephone relays.

The top section of the chassis is normally covered by a removable grey hammerite dust cover with a copy holder on top (missing here).
Driving gear and clutch

The electronic circuits are hidden in the bottom section of the machine. They can be accessed by removing the bottom panel, which is held in place by 4 bolts in the 4 rubber feet. After removing the bottom panel, the electronic parts are exposed immediately. They are mounted on a brown Pertinax panel that is held in place by 5 screws (actually 2 screws, 2 mounting posts and 1 stub).

The electronics section contains the five XOR circuits that are used for mixing a plaintext character with a keystream character. Each XOR is built from discrete components, such as the early OC202 and OC204 silicon PNP transistors.

Other circuits are present for controlling the various solenoids and telephone relays that are part of the mechanical section at the top of the machine. These circuits can be recognised by their large power transistor mounted on a metal carrier at the reverse side of the circuit board. One power transistor is mounted to the frame.
Close-up of the XOR circuits

The circuit board is connected to the rest of the machine via a complex cable tree plus a 50-way D-type connector at the back. After removing the 5 screws, the circuit board can be pulled outwards with the metal grip at the left. This releases the board from the 50-way socket and allows it to be tilted forward, thereby revealing its reverse side. The reverse side contains most of the cabling plus the large 5-to-32 diode matrix that is used to drive the paper strip printer. A smaller 5 x 6 diode matrix is used for the detection of the stunt characters (the discriminator).

Noreen BID/590 Rear view Motor 6-channel tape reader Printer Driving gear and clutch Close-up of one of the solenoids Telephone relais and keyboard 5-bit connector
Bottom view with the electronics exposed The five XOR circuits Close-up of the XOR circuits Some of the driving electronics Power section, used for driving the solenoids Power transistors seen from the rear side of the circuit board Removing the circuit board from the 5-way D-type socket Circuit board folded away from the machine
Large 5 x 32 diode matrix, used for driving the printer Small 5 x 6 diode matrix 5-bit encoder Power transistor mounted to the chassis in order to provide sufficient cooling 50-way D-type socket mounted to the PCB 50-way D-type plug mounted on the chassis 3 diodes Usage counter
The keyboard consists of a total of 32 keys; 31 green spring-loaded letter keys, similar to the ones of the military Teleprinter Model 15, plus a spacebar. Each key is mounted on a metal arm that engages a mechanical 32-to-5 encoding matrix that is located at the machine's bottom side. The encoder identical to that of the Teletype Model 15 and was probably bought as an OEM part.

When pressing a key, its metal arm is moved down and engages 5 metal bars that run from left to right. The 5 metal bars represent the 5 data-bits and each have specific cut-outs that represent the ITA2 telegraphic alphabet.

The cut-outs can cause a bar to slide sideways, or to stay in place. The sideways movement of the bars is carried onto a set of 5 'fingers' that protrude the surface of the machine and finally engage a set of 5 switches that are mounted at the right. Together, these 5 lines form the 5-bit code of the character typed on the keyboard.
Close-up of the keyboard with the indicator lamp visible just above the letter 'M'

When typing, the operator has to wait until the key has been 'processed'. This processing has an arbitrary length and can take up to several seconds as the machine automatically inserts spaces, message indicators and non-printable characters, such as Carriage Return (CR) and Linefeed (LF).

On later version of the Noreen, such as the BID/590/2, an electro­mechanical character counter was added in order to find the approximate end of a line. The letter counter is housed inside a rectangular metal enclosure that is mounted underneath the keyboard. It has a small window at the top through which a bright signal lamp is visible between/below the keys.

When typing, it counts the letters that have been entered since the last CR. When it reaches 59 or 60, the lamp is turned on to indicate that you are approaching the end of line (69 characters).
End-Of-Line indicator

The character counter was added to prompt the user to insert CR and LF characters at the end of a line, so that the resulting plaintext, after decoding on a Rockex, was nicely formatted. The counter is reset automatically by a microswitch mounted under the Carriage Return (CR) key.

If the lamp comes on, the user has about 10 characters left before the end of the current line is reached. It can best be compared to the bell on an old mechanical typewriter did the same.

The image on the right shows the interior of the counter. At the center is a spring-loaded cogwheel that is advanced by a solenoid at the right, each time a character is entered on the keyboard. When the end is reached, a switch will turn on the lamp. When the user presses CR, a microswitch (mounted under the key) will cause the leftmost solenoid to release the cogwheel.
Character counter

The character counter was probably added at a later date, most likely as a specific feature of the BID/590/2 model. It is not present on early versions of the machine [1]. Furthermore, the counter contains a 1N4004 diode which was not yet available in the early 1960s. According to the date stamps on the telephone relays, the Noreen BID/590/2 shown here, was made in or after 1969.

Keyboard Close-up of the keyboard with the indicator lamp visible just above the letter 'M' Mechanical 32-to-5 keyboard encoder Character counter Mechanical counting wheel Character counter mounted underneath the keyboard Character counter mounted under the keyboard Microswitch hidden under the CR key

Noreen prints its output directly on a paper strip, just above the keyboard, that moves from right to left. The paper was supplied on small reels and was approx. 9.4 mm wide, similar to the paper reels used on the American M-209 and the Russian Fialka cipher machines. The reel was placed horizontally in the black paper holder at the right, and led past the black printing head at the left.

Leaving the paper holder at the right, the paper is guided through a metal guide and then past the print head as shown in the image on the right, through the capstan at the top left. The capstan pulls the paper past the print head.

Where the paper passes the left side of the print head, a small hammer is released at the right moment, pushing the paper against the letter wheel. An ink roller at the right ensures that the character is inked before it hits the paper. The print head has two rows: one with letters (front) and one with numbers and punctuation marks.
Testing Noreen's printer

The timing of the printer is guaranteed by a commutator at the rear end. The 32 electric lines from the 5-to-32 diode matrix are each connected to a contact pad of the commutator. As soon as a voltage-carrying contact is met, the print hammer is released. The timing, and hence the letter position, can be fine-tuned with an adjustment screw that is located aside the commutator.

Front view (with paper strip) 1/2 Printer Printing head with pre-gummed paper strip Printer commutator Testing Noreen's printer
Print head
The print head is located at the front of the machine, just behind the keyboard. It has two rows with 32 characters each, and is driven by a motor axle from the rear. The front row of characters contains the letters. The rear row contains the figures and is only used in FIGS-shift mode. The diagram below shows the print head as seen from the top of the machine, in its default position.

At the right is a spring-loaded ink roller that is pressed against the character ring to ensure that it is constantly inked. A blank paper strip is fed from the right, guided below the print head, and then upwards along the left side of the print head, where a hammer is released exactly at the right moment, pushing the paper against the inked character ring. When FIGS-shift is active, a solenoid temporarily moves the print head towards the front of the machine, as shown here:

The table below shows the layout of the print head going clockwise when looking at the print head from the front of the machine. The order of the characters corresponds to the ITA2 table, when all bits are placed in reversed order (i.e. channel 1 → bit 4 and channel 5 → bit 0). The yellow line is the character row that is closest to the front of the machine. The red line represents the shifted characters (FIGS) that are on the rear character ring, as shown in the image above.

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Nul 5 CR 9 SP £ , . LF ) 4 @ 8 0 : = 3 + Enc ? ' 6 % / - 2 Bel Fig 7 1 ( Ltr
Nul T CR O SP H N M LF L R G I P C V E Z D B S Y F X A W J Fig U Q K Ltr

The blue cells are blanks that take the place of the stunt characters. They are actually cut-out from the character ring, so that they appear as a space in the printed output. This way, the end-of-line characters carriage return (CR) and line feed (LF), both of which are used to format the printed output on Rockex, will appear as a SPACE in the output of Noreen's paper strip printer.

 ITA2 character table

The timing of the printer is controlled by a so-called commutator that is mounted at its rear side. It is driven by the same axle as the print head so that its movement is synchronous to the print head. The commutator can be seen as a rotary switch with 32 contacts, one for each character.

The actual operation of the commutator is slightly more complex than what is suggested in the block diagram at the top of this page. As it is not possible to use a diode matrix for a 5-to-32 decoder, it is used in reverse: a 32-to-5 encoder, the output of which (B) is compared to the 5-bit output of the cipher unit (A). As soon as the two are identical (A=B), the hammer is released.

The simplified block digram above shows how the commutator works. The comparator (that senses the A=B condition) consists of 5 individual XOR circuits, the outputs of which are merged in a wired OR. The output of the OR is inverted and then used to drive the hammer solenoid.

Tape reader
Noreen has a non-standard 6-level Creed tape reader, which is mounted at the left rear, in such a way that the tape enters the reader from the right and leaves it at the left of the machine. The drawing below shows the reader when seen from the top right with the tape running upwards.

The reader accepts a tape width of 7/8" or 22.2 mm, which was also used on other 6-level tape readers at the time. The reader has 6 channels: three at either side of the sprocket hole. In order to prevent the tape from being loaded the wrong way around, there is an extra margin at the left.

The image on the right shows Noreen's key tape reader, as seen from the right, with a suitable keystream tape loaded. When enciphering, the tape moves away from the viewer (i.e. towards the left of the machine). In this view, the extra data channel (i.e. the 6th hole) is at the right.
Key tape moving through the 6-channel tape reader

The remaining five channels represent the normal 5 bits of a 5-level punched tape, in ITA2 format. As seen here, the channels are in the order 54321, which means that channel 1 is adjacent to channel 6. As it might be very difficult to find any surviving 7/8" paper tape, the drawing below can be used as a guide when cutting standard 1" (8-level) paper tape to size.

6-channel tape reader 6-channel tape reader Key tape ready for use Key tape entered into the 6-channel tape reader Key tape moving through the 6-channel tape reader Key tape moving through the 6-channel tape reader Tape reader seen from the rear Tape reader

External battery
Noreen was powered by an external 12V/24V DC source that was connected to the fixed 1.5 metre cable that runs from the back of the machine. At the end of this cable is a military CANNON MS3106E-18-1S connector. Although it is known that in some cases Noreen was powered by a mains power supply unit, this was not officially allowed. In order to avoid TEMPEST problems, it was decided that the machine had to be powered by a shielded 12V/24V battery at all times.

The battery came in a wooden box with a removable top lid, that had a shielding wire cage on the inside in order to avoid unwanted emanations. At the side of the wooden box was a CANNON MS3102E-18-1P socket that mated with Noreen's power plug. Inside the box were two power sources: a heavy duty 12V/24Ah lead-acid battery and a light duty 12V/7.5Ah battery that consisted of two 6V batteries connected in series. The pinout of the battery socket is as follows:

Noreen battery socket when looking into the socket in the external battery pack

The image above shows the pin order of the socket on the battery box [3] when looking onto the pins of the male socket. The pins are marked A-H starting at the top right and running clockwise. The two pins at the centre are marked I and J. Thanks to David White for specifying the wiring [3].

Pin Voltage Description Colour
A GND Ground Frame
B +0V Not connected (spare) -
C - Clutch coil, not connected (spare) -
D +0V Heavy duty battery (+) Orange
E -12V Heavy duty battery (-) Black
F +0V Heavy duty battery (+) Yellow
G -12V Heavy duty battery (-) Blue
H +0V Heavy duty battery (+) Green
I -24V Light duty battery (-) Brown
J -12V Light duty battery (+) Mauve

Note that with Noreen all voltages are referenced from the (+) terminal of the large battery. This means that this line is called +0V, whilst the operational voltages are at -12V and and -24V. The main 12V source (i.e. the heavy-duty battery) is used for the moving parts, such as the driving motor, the tape reader, the printer and the solenoids, whilst the light-duty battery provides the extra voltage needed for the electronic circuits that are mounted at the bottom side of the unit.

As original batteries are no longer present and suitable alternative batteries will be large and cumbersome, it might be best to build a small modern PSU for demonstration purposes. As part of the restoration of the machine shown here, we've built a suitable small electronic PSU that measures no more than 20 x 20 x 10 cm. It has a 10-pin CANNON socket at the front, so that Noreen can be connected directly. At the rear it has a 3-pin socket for connection to the mains.

Power connector Suitable replacement PSU PSU rear view Suitable PSU Noreen and replacement PSU
Sensing switch
The keystream tape supply reel, is normally attached to the right side of the machine, in such a way that the random paper tape can be fed directly to the tape reader at the top left. In order to allow the machine to discriminate between cipher and decipher tape, each type had a different width of the tape core. The supply reel mechanism containes a switch that senses which type of tape core is present. This switch is connected to the 3-pin Bulgin male socket at the rear:

July 2015

When we acquired Noreen in January 2015, the machine was in pretty bad condition. It was clear that the machine had seen some action (as indicated by the usage counter under the tape reader) and it had accumulated quite a bit if dust and dirt in the 30+ years that it had been in uncovered storage since it was decomissioned in the early 1980s. In other words: it badly needed attention.

As this was the first historical British cipher machine in our collection, we were determined to get it going again. Ideally, we would like to be able to use it for demonstrations. After cleaning the mechanics and applying a fresh drop of oil here and there, we made a list of missing things.

The largest missing part is the top case shell which normally covers the machine's mechanical parts. Although we will probably never find this part, we do not consider it a problem. Noreen can be used perfectly well without it, and it gives us the opportunity to see its beautiful inner life.
Noreen BID/590

As you can see in the image above, one of the key tops (the letter 'Z') was missing, just like the red lens of the upper indicator light to the left of the keyboard. Both items would be difficult to find. The paper feed tray for the strip printer (not shown here) came without its transparent top lid, but again this was not considered a problem as the machine can be used without it.

Another challenge was the uncommon key tape reader, which requires a 6-channel paper tape, rather than a more common 5-channel or 8-channel one. Consequently, it needs very rare paper tape with a width of 7/8". Apart from that, the key tape format was largely unknown to us.

The latter problem was solved with help from the Crypto Collectors News Group on Yahoo. After long in-depth discussions we were able to define the tape format with reasonable certainty. And after a tip from one of the members, we were able to secure some suitable tapes on eBay.
Red indicator lamp

In the following weeks, we found the missing key top, again on eBay. Luckily, the key tops of the Noreen are identical to the ones that are used on the military variant of a Teletype Model 15. And at the HAM RADIO 2015 in Friedrichshafen (Germany), we found the missing red indicator light.

In the meantime, we had built a small power supply unit that could be connected directly to Noreen, instead of the complex battery unit that was, of course, missing as well. When we powered Noreen up after a sleep of 30+ years, the electronics worked surprisingly well and we were soon able to type our first clear message.

As the key tape feeder (another missing part) has a built-in switch that senses whether an encryption or decryption key tape is present, we had to make a dummy cable with a slide switch that simulates the sensing switch of the feeder.
Key tape in secured can

Now the time had come to encode or decode our first real message. Whilst we were in Friedrichs­hafen, a package had arrived in the mail. Inside it was a small can with a short key tape. It was created by Richard Girling, one of the members of the Crypto Collectors News Group, and should be used in combination with the ciphertext message he had sent previously via regular e-mail.

After some further cleaning of contacts and testing with various in-house created key tapes, we connected the dummy cable and set all switches to Decode (DE). Then, after making a few corrections to Richard's key tape, we loaded it into the tape reader and were able to decrypt our first Noreen message. Perhaps you can imagine the joy we felt when we saw readable plaintext appearing on the narrow paper strip.

As you can see, the printer sometimes 'forgets' to advance the paper, resulting in a double character, but this issue will be dealt with later.
The ciphertext message and key tape provided by Richard Girling, along with the decrypted ouput.

Next we tried to Encode (EN) a message and this worked flawlessly. Any character can be used in the plaintext, and the ciphertext is nicely formatted in groups of 5 letters (A-Z) each, separated by spaces. Not only does this mean that Noreen is working correctly, it also proves that the key tape format was deduced correctly. Many thanks to all who have contributed to this result.

Noreen BID/590 Usage counter Suitable replacement PSU Key tape supply reel simulator Red indicator lamp Left side of the keyboard, showing the replacement 'Z' key top and the red indicator light Key tape in secured can Decoded message
Known locations
  1. The exhibition in Hut 1 was closed down in September 2013. Current whereabouts of the Noreen are unknown.

Crypto Museum are currently looking for the following Noreen-related items:
  • Key top for the letter 'Z'
    Update April 2015: Found in the US.

  • Red lens for indicator light
    Update June 2015: Found in Germany.

  • Metal top cover

  • Copy holder

  • 6-level paper tape
    Update May 2015: Found in the US.

  • Key tape feeder
    External assembly mounted at the right side of the machine (with built-in tape sensing switch).

  • Transparent cover for printer supply reel
    This is the transparent cover that sits on top of the horizontally placed printer strip supply reel, to the right of the printer.

  • Documentation
    Any documentation about Noreen BID/590 would be most welcome.
  1. Jerry Proc's crypto pages, BID 590 (Noreen)
    Website. Retrieved January 2015.

  2. Wikipedia, Rockex
    Retrieved January 2015.

  3. David White, Personal correspondence
    January 2015.

  4. ECMA, Standard ECMA-10 for Data Interchange on Punched Tape
    2nd Edition. July 1970.

  5. ITT Cannon GmbH, MS3106E18-1S Datasheet
    Noreen-side power plug. 4 January 2015.

  6. ITT Cannon GmbH, MS3102E18-1P Datasheet
    Battery-side power socket. 4 January 2015.

  7. Frode Weierud, Discussion on the operation of the XOR circuit
    Crypto Collectors Newsgroup. May 2015.

  8. Rufus L. Taylor, Disclosure of Details of ROCKEX to the French
    Ref ID: A61029. USCIB: 39.2/10. 20 September 1954. SECRET.
    Declassified by the NSA on 21 April 2014 (EO 13526).
Further information
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Crypto Museum. Created: Tuesday 13 January 2015. Last changed: Friday, 30 December 2016 - 10:02 CET.
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