Protection for software in measuring instruments
Introduction
A basis of modern measuring instruments is microprocessor that controls all functions of the instrument. Thus software of this microprocessor imminently affects not only functions of the instrument but also its parameters because measured signals are processed by means of its program. Hence the software should be properly protected against accidental and also intentional unauthorized change. A principle of this protection would be the integrity check—not only for control program itself but especially for all data, i.e. correction and calibration coefficients. These data are preferred to be stored separately, out of control program, by reason of easy calibration of the instrument.
The protection against software copying is understood as subsidiary problem because the reengineering and copying of the measuring instrument is distinctively more complicated a problem than copying a control program only.
Section snippets
Feasible solutions
The integrity check can be performed by many ways. One of the usually used possibilities is application of the cyclic codes—CRC that are utilized at data transmission. Another, more exacting possibility is the utilization of hashing functions that are used in various cryptosystems.
The cyclic codes create an extensive group of the safety codes. Their advantage is excellent protection characteristics and easy technical realization. Mathematical calculation is firstly based on dividing of a
Realization
Above mentioned knowledge was applied for proposal of microprocessor core of the electronic load control system. The control program allows the software and correction data update provided by end user. Demands for microprocessor capacity are relatively low so the powerful 8-bit microprocessor still can be used. The control program size was estimated at minimum 32 kB. The correction data size would be maximum 8 kB. That is why relatively simple solution (see block diagram at Fig. 1) was
Conclusion
The protection of instrument control software using the algorithm HMAC-MD5 was successfully realized in control system of electronic load device. This control system is equipped with microprocessor DS89C420 see Ref. [7].
The utilization of microprocessor with considerably higher performance capacity enables to perform integrity check by means of algorithm HMAC-MD5 without larger problems. In the case of higher safety requirements, an algorithm HMAC-SHA-1 can be used with increased demand of
Ing. Ales Vobornik, PhD was born in Liberec, Czech Republic, in 1964. He received his BS Ing. in Electrical Engineering from the VSSE in Pilsen, CZ in 1988. He worked in Locomotive plant, Skoda Co. during 1988–1992 as a R&D engineer. In 1992 he became a lecturer at Faculty of Electrical Engineering, University of West Bohemia, Department of Electrotechnology and Measurement Technology. He received his PhD degree from the University of West Bohemia, CZ in 2000. His research interests include
References (7)
- R. Rivest: rfc1321, MIT Laboratory and RSA Data Security,...
- M. Oehler, NSA—R. Glenn, NIST: rfc2085,...
- H. Krawczyk, IBM—M. Bellare, UCSD—R. Canetti, IBM: rfc2104,...
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Ing. Ales Vobornik, PhD was born in Liberec, Czech Republic, in 1964. He received his BS Ing. in Electrical Engineering from the VSSE in Pilsen, CZ in 1988. He worked in Locomotive plant, Skoda Co. during 1988–1992 as a R&D engineer. In 1992 he became a lecturer at Faculty of Electrical Engineering, University of West Bohemia, Department of Electrotechnology and Measurement Technology. He received his PhD degree from the University of West Bohemia, CZ in 2000. His research interests include study of control electronic measurement instruments.