CZ-1 Encryption unit; manufactured by Brown Boveri.

The CZ-1 electronic encryption system was developed by Brown Boveri to encrypt the communication of R-902 and R-915 microwave relay systems and was introduced in 1987 and remained in use until 1999, when it was replaced by the BSG-93.

• Principle: Encryption unit
• Operation modes:
• Bit rate: 512c or 2048 kbit/s
• Key: 2 (input via keyboard, automatic or key gun)

• Mains operation: 176 - 264 V, 15 VA
• Batteries: 20 - 33 V, 14 W

• 328 x 445 x 466 mm, 19 kg, in case 430 x 530 x 270 mm, 28 kg

• Accessories case CZ-1/ZUK with power distribution and cable connection box, cables, operating instructions

The CZ-1 encryption unit is used for the electronic encryption of microwave relay connections. The R-902 microwave communications system got enhanced „in combat value“ with the new MK-7 multi-channel adaptor and the CZ-1 encryption unit. This successful combination was also used again in the successor system, the R-915 microwave relay system.

The key can be entered using the keypad; for a two-way connection, the set has the option of automatic key generation: the system itself creates an active, a reserve and an operational authentication key and uses these for the communication on the point-to-point connection. Not even the operating personnel can read the automatically generated key. The next time contact is made, the reserve key is used as the active key and a new reserve key is generated.

At the microwave relay station, the CZ-1 is connected to the multiplexer on the „clear“ side. The multi-channel multiplexer forwards the bit rate information to the CZ-1 and synchronisation with the remote station is done at the beginning of each transmission in form of a start synchronisation. Synchronisation signals are only transmitted during an ongoing transmission if the connection is interrupted.

The three encryption keys, the active, reserve and operating authentication keys, remain stored in the CZ-1 for three days even if the power supply is interrupted, after which they are automatically deleted. An identical initial authentication key (IAS) entered on both sides ensures that only two „friendly“ sets communicate with each other. Only in emergency mode is it possible to work without IAS for 30 minutes.

In normal operation, the IAS is entered on both sides and an initial key is generated using ASE (automatic key generation). This first key is combined with the IAS; if the two keys are identical, the two CZ-1s are synchronised. ASE can then be used to generate an active key, a reserve key and an operational authentication key. The entire key generation process takes 20 seconds; five seconds after starting the process, encrypted operation can already begin.

With function 2 (handshake), two CZ-1s are connected directly together using the LAK cable and the three keys are generated using ASE. These keys are retained in the sets even when the power supply is switched off. From then on, the sets are transported to the locations where they are used, but as the sets now contain active keys, the sets themselves have to be kept secret from that moment, the keys are generated.

A field telephone connection on service channel 1 is provided for an unsecured service connection with the remote station.

The clear signal is mixed in the key modulator with a key signal from the key computer by performing a bit-by-bit modulo-2 addition. On the receiving side, the ciphertext is subjected to the same operation with the key signal from the key computer, which restores the plaintext. Both key computers are able to produce the identical pseudo-random key signal with the same basic settings.

The same basic key settings must exist at the sending and receiving points on both computers, and the same key settings are also used at both points for transmission in the opposite direction. However, the keys for the „return path“ are completely different from those for the outgoing path.

In the MK-7 multi-channel multiplexer, the clear data, the associated clock and the synchronisation status signal are provided on both sides for the CZ-1 coding device.

The CZ-1 is designed entirely in semiconductor technology.

The CZ-1 was developed by Brown Boveri in 1984/85 under company designation Vericrypt 5000 and the encryption system was introduced in 1987 as part of the R-902 combat upgrade through encrypted operation (RIMUS) and procured until 1989.

• Chiffrierausrüstung CZ-1,Brown Boveri & Cie, German, French.
• Die Chiffrierausrüstung CZ-1, Regl 58.113d, German
• Chiffriergeräte CZ-1 und CZ-2, ALN 619-5555

• CZ-1 on the Hamfu website