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DMR
Digital Mobile Radio - this page is a stub

Digital Mobile Radio (DMR) is a a standard for digital mobile two-way radio communication, set in 2005 by the European Telecommunications Standards Institute (ETSI) and endorsed by the DMR Association [1][2]. It was developed to be low-cost and easy to use. Like P25 II it uses two-slot Time-Division Multiple Access (TDMA) in a 12.5 kHz channel 1 with the AMBE+2 vocoder [2]. Equipment that supports the DMR standard is assumed to be interoperable with equipment from other manufacturers. The DMR standard was enhanced in 2012 with trunking capability.



  1. One slot uses the equivalent bandwidth of 6.25 kHz. In comparison, NXDN uses discrete 6.25 kHz channels, whilst TETRA uses a four-slot TDMA in a 25 kHz channel.

DMR Tiers
  1. Licence-free PMR446 use (2005)
    Products for licence-free use inthe Euopean PMR446 band. To be used without an existing infrastructure (repeaters) for low-power commercial applications. The maximum RF output is 0.5 Watt.

  2. Conventional licenced use (2005)
    Products for licenced conventional radio systems operating in the PMR frequency bands between 66 and 960 MHz. Targeted at users who require spectral efficiency, advanced voice features, integrated IP data services and high power output.

  3. Trunking network (2012)
    Trunking operation in the 66-960 MHz frequency bands. It supports voice and short messaging handling similar to TETRA, and packet data service in a variety of formats, including IPv4 and IPv6.
Standards
  • TS 102 361-1
    Air Interface Protocol
  • TS 102 361-2
    Voice and General services and facilities
  • TS 102 361-3
    Data protocol
  • TS 102 361-4
    Trunking protocol
Encryption
By default, DMR is not secure. Although eavesdropping is more complex than with analogue radio systems (e.g. FM), there are radio scanners on the market that can readily decode a DMR audio stream. For enhanced security, some manufacturers offer encryption as an additional feature [3]. The following types of encryption are currently recognised:

  • Basic encryption
    This is the simplest implementation that is basically a voice scrambler that is intended for analogue mode operation. It uses a 10, 32 or 64 character KEY. Note that voice scramblers are inherently insecure.

  • Enhanced encryption
    This type of encryption is endorsed by the DMR Association and uses ARC4 with a 40-bit key. Although it offers better security than Basic Encryption (see above), A 40-bit key is considered insufficient by today's standards (2023). As a result, a brute-force attack is considered realistic. Several attacks against RC4/ARC4 are known [4].

  • Advanced encryption
    This encryption type uses the Advanced Encryption Standard (AES) with a 128 or 256 bit key. AES was established in 2001 by the US National Institute of Standards (NIST) and is considered very secure.

  • Customised encryption
    This type of encryption allows the use of a proprietary encryption algorithm by installing a customised SIM or SD card in the radio.
Manufacturers
Documentation
  1. Digital Mobile Radio (DMR) leaflet
    Undated.
References
  1. Wikipedia, Digital mobile radio
    Visited 2 November 2023.

  2. Wikipedia, Multi-Band Excitation
    Visited 4 November 2023.

  3. Security and Encryption
    Hytera Europe, 12 September 2018.

  4. Wikipedia, RC4
    Visited 4 November 2023.
Further information
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© Crypto Museum. Created: Thursday 02 November 2023. Last changed: Thursday, 16 November 2023 - 08:02 CET.
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