Michal Sramka

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Huge amounts of movement data are automatically collected by technologies such as GPS, GSM, RFID, etc. Publishing such data is essential to improve transportation, to understand the dynamics of the economy in a region, etc. However, there are obvious threats to the privacy of individuals if their trajectories are published in a way which allows(More)
Data sanitization has been used to restrict re-identification of individuals and disclosure of sensitive information from published data. We propose an attack on the privacy of the published sanitized data that simply fuses outputs of multiple data miners that are applied to the sanitized data. That attack is practical and does not require any background or(More)
We present group-theoretic and cryptographic properties of a generalization of the traditional discrete logarithm problem from cyclic to arbitrary finite groups. Questions related to properties which contribute to cryptographic security are investigated, such as distributional, coverage and complexity properties. We show that the distribution of elements in(More)
Published data is prone to privacy attacks. Sanitization methods aim to prevent these attacks while maintaining usefulness of the data for legitimate users. Quantifying the trade-off between usefulness and privacy of published data has been the subject of much research in recent years. We propose a pragmatic framework for evaluating sanitization systems in(More)
We analyze and critique the public-key cryptosystem, based on combinatorial group theory, that was proposed by Wagner and Magyarik in 1984. This idea is actually not based on the word problem but on another, generally easier, premise problem. Moreover, the idea of the Wagner-Magyarik system is vague, and it is difficult to find a secure realization of this(More)