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CSE-280
Encrypted VHF transceiver · CRYPTOVOX

CSE-280 is a VHF radio transceiver with digital voice encryption, introduced in the early 1970s by Crypto AG (Hagelin) in Zug (Switzerland). The 2-piece set consists of an SE-035 VHF transceiver and a CV-096 digital speech encryptor. The crypto-algorithm 1 was developed by the German cipher authority ZfCh, which makes it readable 2 by German and American intelligence services.

The device was intended for use on short and medium range VHF radio links, such as the ones used by military reconnaissance units, and came in two parts: A large 500-channel VHF radio set with digital frequency selection, and a half-hight digital voice encryptor, mounted to its bottom. A selective call system allows Up to 81 users to be addressed individually, in nine separate groups.

The complete kit is shown in the image on the right. The set was mounted in a metal frame, suitable for vehicle use, or in a canvas webbing kit, allowing it to be carried around in the field.
  
CSE-280 in metal frame

The transmitter has an output power of 3W or 20W in the VHF-L band, and is ideal for use in short and medium range military reconnaissance networks, and high-security governmental communications, for example in police investigations, or in foreign embassy communications.

CSE-280 was the first voice encryption product made by Crypto AG. It uses Delta Modulation and true digital encryption – based on shift-register technology – that was developed at the German Zentralstelle für das Chiffrierwesen (ZfCh) in Bad Godesberg (near Bonn, Germany). It contains an exploitable weakness (backdoor) that makes it readable for ZfCh (and later also NSA). The device was used by the armies of several countries, including Syria (see below). A secure (unreadable) version was developed in 1976. The CV-096 was succeeded in 1976 by the smaller CVX-396.

  1. At least two versions of the cryptographic algorithm exist: the initial one, developed by ZfCh, which is readable, 2 and an improved one, developed in 1976 by R&D chief Peter Frutiger, which is unreadable.
  2. The term readable means that the algorithm could be broken by ZfCh. Also known as friendly or insecure or exploitable. In contrast: algorithms that are not breakable by ZfCh, are called unfriendly or unreadable.

CSE-280 mounted in metal frame CSE-280 in metal frame Frontal view CSE-280 Accessory bag at the rear CSE-280 with handset Handset Speaker
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CSE-280 mounted in metal frame
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CSE-280 in metal frame
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Frontal view
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CSE-280
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Accessory bag at the rear
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CSE-280 with handset
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Handset
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Speaker

Features
The diagram below shows a complete CSE-280 system, mounted in a metal frame with rubber shock-mounts, ready for installation in a vehicle. The set is powered by the 12V or 24V battery of the vehicle, which should be connected at the rear. All other connections and controls are at the front. The set is enabled with the POWER selector on the transceiver (OFF, Stand by, 3W or 20W), whilst the desired mode of operation (plain, crypto or repeater) is set with the MODE selector.

Three thumbwheels are used to select any of the 500 available channels. Furthermore, two thumbwheels are used to select a remote address. The first digit selects the group, whilst the second digit sets the sub-address. A '0' selects all users in that group (e.g. '80'), whilst '00' is used for a general broadcast. The local address is defined by a code-plug (43 in this case).

CSE-280 seen from the front

The lower unit is the actual voice encryptor. It is powered by the transceiver, via a short cable at the rear. Data is transferred via another short cable at the front panel. The encryption key is set with 8 thumbwheels (108 possibilities). In addition, a family-key can be set internally, providing a total key space of 1032 possibilities. A total of four keys can be stored in the internal memory.

Using the CSE-280 in the field Frontal view Front panel CSE-280 with wiring installed LEMO connectors Selecting a key comaprtment Code-plug on the SE-035 transceiver Voltage selector (12/24V)
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Using the CSE-280 in the field
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Frontal view
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Front panel
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CSE-280 with wiring installed
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LEMO connectors
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Selecting a key comaprtment
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Code-plug on the SE-035 transceiver
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Voltage selector (12/24V)

History
Development of the CSE-280 was started in the late 1960s, at a time when the company was still owned by its founder, Boris Hagelin. But as there were strong ties to the American and German intelligence services, it was decided that the German cipher authority – the Zentralstelle für das Chiffrierwesen (ZfCh) – would design the
cryptologic
(the part that holds the crypto-algorithm). It was developed in parallel with the MCC-314 bulk encryptor, which uses a similar
cryptologic
[3]. The device was made with help from Siemens and was introduced during the course of 1971.

The algorithm had a built-in weakness that was designed by experts at the ZfCh [3]. It made the device readable to them (ZfCh) and later – after Crypto AG had been purchased by the BND and CIA – also to the American National Security Agency (NSA), giving them an obvious advantage.

But in late 1976, the NSA suddenly discovered that they were no longer able to read intercepted traffic from the Syrians. Apparently the Syrians had become aware of weaknesses in the algorithm and had complained to Crypto AG, where head of the R&D department – Peter Frutiger – provided them with a fix that caused it to become unreadable (unexploitable). Frutiger got fired for this [3].

 More history


Parts
Wooden transport case Metal mounting frame VHF transceier SE-035 Speech encryptor CS-096 Handset Speaker Data, audio and power cables
Storage case
The vehicle variant of the set – mounted in a green metal frame – was supplied in a wooden transport case, with metal grips at either side.

When the set is not used for an extended period of time, or when it is stored in a depot, it was generally stowed in the wooden container shown in the image on the right.
  
CSE-280 storage case

Mounting frame
The image on the right shows the SE-035 VHF transceiver and the CV-096 encryptor, mounted with four rubber shock-mounts in a green metal frame, ready for installation in a vehicle. At the rear is a canvas pocket in which the accessories and cables can be stored.

The set can also be removed from the frame and placed on a desktop, in which case a metal bracket at the bottom of the lower unit, allows the set to be tilted.
  
CSE-280 mounted in metal frame

VHF transceiver   SE-035
The largest of the two units is the SE-035 VHF transceiver. It provides 500 channels with a channel spacing of 25 kHz in the VHF-L band, between 29.3 and 41.7 MHz, although other frequency ranges were available on request.

The transceiver has a selective call system that allows up to 81 users, in groups of 9 users each. The address of the local station is contained in a code plug, whilst the address of the remote station is selectable with thumbwheels.
  
SE-035 VHF transceiver

Speech encryptor   CV-096
The actual encryptor is a separate unit, known as CV-096, which is usually mounted to the bottom of the transceiver. It is connected to the radio by means of two short cables: one at the rear that provides power, and one at the front that carries the digital data to and from the encryptor.

At the start of a transmission (i.e. when the PTT is depressed) the encryptor generates a new unique sequence, to which the other end must synchronise before speech is reproduced.
  
CV-096 voice encryptor

Handset
The transceiver is usually operated with the handset shown in the image on the right. It is connected to the transceiver by means of an 8-pin LEMO connector that mates with the handset socket on the front panel of the transceiver.

The handset has a built-in Push-To-Talk switch (PTT) in the grip, that has to be pressed to enable the transmitter.
  
Handset

Speaker
The transceiver does not have a built-in speaker, and relies on an external handset, such as the one shown above, or a headset, or the external speaker, shown in the image on the right.

The speaker can be used in combination with the (optional) handheld microphone. It can also be used in combination with the handset, as an additional monitor.
  
Speaker

Cables
All interconnections between transceiver and encryptor, and connections to the peripherals, are by means of high-quality connectors from the Swiss manufacturer LEMO, as shown in the image on the right. When unused, they are stowed in a canvas pocket at the rear.

A thick cable provides power from an external battery to the transceiver, whilst a short one loops the power to the encryptor. At the front, another loop cable connects the encryptor to the data socket of the transceiver.
  
Cables

CSE-280 storage case CSE-280 mounted in metal frame Stacked SE-035 transceiver and CV-096 voice encryptor SE-035 VHF transceiver CV-096 voice encryptor Handset Speaker Cables
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CSE-280 storage case
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CSE-280 mounted in metal frame
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Stacked SE-035 transceiver and CV-096 voice encryptor
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SE-035 VHF transceiver
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CV-096 voice encryptor
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Handset
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Speaker
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Cables

Specifications
Transceiver   SE-035
  • Frequency
    29.3 - 41.7 MHz
  • Channels
    500
  • Spacing
    25 kHz
  • Bandwidth
    6 kHz ±3dB
  • Modulation
    FM
  • Impedance
    50 Ω
  • Output
    3W or > 20W
  • Sensitivity
    < 0.7µV
  • Power
    12V or 24V
  • Current
    12V: 1/4.5A, 14V: 0.5/2.2A
  • Dimensions
    375 x 240 x 100 mm
  • Weight
    8 kg
Encryptor   CV-096
  • Modulation
    Modified multi-level delta-modulation
  • Clock
    9600 Hz
  • Variations
    1032
  • Keys
    108
  • Power
    12V or 24V
  • Current
    12V: 1A, 24V: 0.6A
  • Dimensions
    375 x 240 x 70 mm
  • Weight
    5 kg
Options
  • Headset
  • Handset
  • Speaker
  • Handheld microphone with PTT
  • Remote control unit
  • Telephone dial adapter
  • SWR meter
  • Rod antenna
  • Mast antenna
  • Car mounting kit
  • Power supply unit
  • Portable battery
  • Repeater adapter
Documentation
  1. CSE-280 Brochure (German)
    Crypto AG. FGG 250 1373b/5. Date unknown.
References
  1. Crypto AG, Company brochure
    Date unknown, but probably 1976. 24 pages. p.9.

  2. Oskar Stürzinger, Chiffriertechnik Heute
    Vorlesung Krieg im Aether 1976/1977, ETH Zürich (German). p.31. 1

  3. Crypto Museum, Operation RUBICON
    February 2020.
  1. Retrieved from HAMFU History, December 2018.

Further information
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Crypto Museum. Created: Wednesday 01 January 2020. Last changed: Monday, 10 February 2020 - 15:03 CET.
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