What is a Digital Tachograph?
A digital tachograph is a control device for road transport.
The digital tachograph is composed of a Vehicle Unit (VU) essentially containing a printer, two slots for the cards and a display, and a sensor connected to the gearbox. The VU is the brain of the system. It is able to hold data on drivers of the vehicle and their periods of driving and duty for about a 12 month period. It also and notably holds data relating to faults, attempts to tamper with the system, over speeding, calibration details, and when data has been accessed, for example, by the Police.
The VU and the motion sensor from the gearbox are paired and the signals from the sensor are fully encrypted so that any attempt to interfere with them is registered and recorded in the vehicle unit. The VU is set to Universal Time Co-ordinated (UTC) – as another name for Greenwich Mean Time (GMT) - all records are against this time. The visual display can be set to the local time, but this does not affect the internal time.
It functions with smart cards. Drivers, companies (operators), workshops (tachograph calibration centres) and enforcement officers (police for example) are issued with smart cards according to their specific needs. These enable them to use and / or give access to the data in the VU.
Recording Equipment & Vehicle Unit
Distinction has to be made between:
- The recording equipment which includes cables, a motion sensor, and a vehicle unit; and
- The Vehicle Unit that includes a processing unit, a data memory, a real time clock, two smart card interface devices (for driver and co-driver), a printer, a display, a visual warning, a calibration/downloading connector, and facilities for entry of user’s inputs.
Whenever the words “digital tachograph” are used, it has to be understood as recording equipment.
Digital Tachograph Security
In order to allow a full compatibility between any VU and any tachograph card on one hand, and allow any controller to inspect data downloaded from any VU on the other, some security mechanisms have to be common and fulfil the following security requirements:
- Mutual authentication between VU and cards,
- Integrity and authentication of data transferred between VU and cards,
- Integrity and authentication of data downloaded to external storage media.
Security mechanisms are closely related with security elements (e.g. cryptographic keys) and distribution methods. Both security mechanisms and security elements had to be defined together.
Main constraints encountered by digital tachograph component manufacturers are the following:
- Tachograph components are distributed in the field and are not connected on-line to any central register for checks,
- Different manufacturers and different issuing authorities are involved,
- The introduction of digital tachograph will occur step by step both in new member States and from new manufacturers,
- Security parameters rely on leading edge but currently available and proven Information Technology,
- Security parameters must allow to periodically up-grade security elements.
Security targets are defined by so-called Security Enforcing Functions (SEF). SEF are required for the digital tachograph components (motion sensor, Vehicle Unit (VU) and tachograph smart cards). An independent laboratory approved for ITSEC (Information Technology Security Evaluation Criteria) evaluations declared SEF used for digital tachograph as suitable, complete and appropriate for ITSEC E3 evaluation.
Cryptographic information technology provides security mechanisms able to fulfil authentication and data integrity requirements. Authentication requirement implies that any element of the system (VU, card) must be able to prove to any other element of the system that it belongs to the system. Data integrity guarantees that only authorised persons can access data.
Keys and Certificates
For the digital tachograph application, keys are distributed at three levels:
- European level,
- Member State level,
- Equipment Manufacturer or Card Personalisation level.
Beside cryptographic keys, the security system is based on certificates distributed at three levels afore-mentioned.