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Motorola Key Variable Loader

The KVL-3000 (or T5795A) is a device for loading cryptographic material (key variables) into a series of two-way radios, developed and produced by Motorola (USA) around 2001. The device can be used for a variety of cryptographic algorithms and is compatible with a range of radios.

A Key Variable Loader, or KVL, is commonly known as a Key Filler or Fill Gun, and generally uses a proprietary data protocol for transferring cryptographic material (keys) to the radio.

Initially, Motorola had a separate Key Variable Loader (KVL) for each individual cryptographic algorithm, such as DVP, DES and DES-XL, but these were eventually all replaced by the KVL-3000 and the KVL-3000 Plus. The difference between these two versions is that the earlier KVL-3000 has a 4-line 12-character display, whilst the Plus has a bitmap (matrix) display.
Operating the KVL-3000

The KVL-3000 has two modes of operation: Advanced Securenet (ASN) and ASTRO 25. ASN mode is needed, for example, for loading keys into the older SABER I, II and III hand-held radios. The required mode can be selected via the CONFIG menu. A special cable, that is different for each type of radio, connects the Keyload I/O port at the rear of the KVL to the accessory socket of the radio. The case design of the KVL-3000 is patented by Motorola.

Complete KVL-3000 kit
Operating the KVL-3000
IR port and serial connection
Serial connection (RS232)
Performing a self-test
KVL-3000 ready for use
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Complete KVL-3000 kit
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Operating the KVL-3000
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IR port and serial connection
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Serial connection (RS232)
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Performing a self-test
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KVL-3000 ready for use

 Loading keys into a Motorola SABER radio

  • KVL-3000
    This is the initial version of the KVL-3000. It has a display with 4 lines of 12 characters each, plus a row of icons at the top. It can be used for loading key variables for the common Motorola encryption algorithms: DES, DVP, DES-XL, DVP-XL and DVI-XL. 1

  • KVL-3000 Plus
    This is a slightly later version of the KVL-3000 that is equipped with a matrix display (bitmap), allowing icons and graphics to be displayed. This version is suitable for all of the earlier protocols 2 plus AES-256 and DES-OFB. Please note that this version does not support the DVP encryption algorithm (it does support DVP-XL however).
  1. Please note that only two algorithms can be installed in a KVL-3000 at the time of ordering, and that many of them come with just one algorithm installed (DES). Be aware of this when buying via eBay.
  2. Although the KVL-3000+ can be loaded with support for multiple encryption algorithms, there is no guarantee that all algorithms are present. Check which algorithms are present, before buying it.

  • Password protection (operator and supervisor)
  • Can hold up to 1024 encryption keys (traffic keys and shadow keys)
  • Menu-driven User Interface
  • Software upgrades via PCMCIA card slot and Motorola FLASHportTM
  • Various encryption algorithms (see above)
  • Various encryption protocols (see above)
  • Supports various FIPS encryption standards (see above)
  • RS-232 and Keyload I/O ports
  • Supports serial and PCMCIA modems
  • Key sharing between KVLs
  • Event log of KVL activities
  • Supports transfer to/from Key Management Controller (KMC)
The KVL-3000 is backwards compatible with the following Key Variable Loaders. Please note that the model number normally has a letter suffix, for example T3010AX, which indicates the revision. The higher the letter, the more features the key loader supports.

  1. First generation.

Supported algorithms
Supported protocols
  • 12 Kb/s SECURENET ™
  • 9.6 Kb/s Secure ASTRO ™, with VSELP Vocoder
  • 9.6 Kb/s Secure APCO Project 25 (IMBE Vocoder)
Supported standards
ASN   Advanced Securenet
CFB   Cipher Feedback
A block cipher mode that enhanced ECB mode by chaining together blocks of cipher text it produces, and operating on plaintext segments of variable length, less than or equal to the block length.
DES   Data Encryption Standard
Universal encryption algorithm developed in the mid-1970s by the US National Security Agency (NSA) for the protection of voice, data and financial transactions. Although initially intended for use exclusively by the US Government, it ws later released for use by the general public.  More  Wikipedia
DVP   Digital Voice Privacy
Motorola's own proprietary voice encryption system, based on a self-synchronising Cipher Feedback (CFB) principle. The algorithm is also known as Digitial Voice Protection.  More
ECB   Electronic Codebook
A block cipher mode in which a plaintext block is used directly as input to the encryption algorithm and the resultant output block is used directly as cipher text.
FIPS   Federal Information Processing Standard
KVL   Key Variable Loader
OFB   Output feedback
a block cipher mode that modifies ECB mode to operate on plaintext segments of variable length lesss than or equal to the block length.
Related patents
  • US5363447 (key loading) - 26 March 1993
    Method for loading encryption keys into secure transmission devices. This patent describes how encryption keys (typically DES, DVP, DES-XL, DVP-XL or DVI-XL) are loaded into a device (radio) and how they are protected against evesdropping. The latter is done by using a Key Encryption Key (KEK) generated by an internal free-running counter.

  • US4167700 (DVP)- 2 May 1977
    Digital Voice Protection System and Method. A description of Motorola's own proprietary encryption algorithm, known as DVP.

  • USD390554 (KVL 3000) - 31 May 1996
    This patent protects the (case) design of the later KVL-3000 Key Variable Loader (key filler). It was a universal device that could be used to load virtually any type of key into any type of (crypto-capable) Motorola radio.
  1. Motorola, KVL 3000 and KVL 3000 Plus Key Variable Loader
    User's Guide. 68P81131E16-A. 1 October 2001.

  2. Motorola, KVL-3000 Specification Sheet
    February 2003. 4 pages.
Further information
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Crypto Museum. Created: Friday 08 March 2013. Last changed: Monday, 22 August 2022 - 13:36 CET.
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